Midterm Flashcards
(246 cards)
1
Q
Explain how egg and sperm join make human chromosomes
A
You get 23 Chromatids or chromosomes unpaired from mom and 23 Chromatids or chromosomes
unpaired Chromatids or chromosomes unpaired from dad. When they fertilize (join) each chromatid
finds their sister chromatids (identical pair) to make a chromosome pair.
2
Q
What are the two states that cells in the body alternate between?
A
Division & non-division
3
Q
How are Red blood cells formed?
A
bone marrow cells pass though the cell cycle continually to form red blood cells (RBCs)
4
Q
Why do cells need to divide?
A
- In embryonic period to make sure you have enough cells to develop
- Because cells have a shelf life and they will eventually die so they need to divide so you will always have the correct amount of cells
5
Q
What is the sequence of events from one division to another called?
A
Cell cycle
6
Q
What are the three phases of somatic cells?
A
Interphase
Mitosis
Cytokinesis
7
Q
What is cytokinesis?
A
Division of the cytoplasm
8
Q
What is Mitosis?
A
Division of the nucleus lasts about 1-2 hours
9
Q
What is interphase?
A
Interphase is the longest phase & is a period of non-division. It is bulking up in order to get ready for division. 18-24 hours
10
Q
What occurs in G2 of interphase?
A
G2 or gap 2
It is the phase following DNA duplication and the last phase before mitosis. A second period of cellular growth occurs, mitochondria divide and precursors of spindle fibers are formed. By the end of G2 the cell is ready to divided (mitosis)
11
Q
What occurs in S of interphase ?
A
S or Synthesis:
Duplication this is when the two identical daughter DNA molecules of each chromsomes occurs. DNA is replicated and doubles. Chromosomes are very long and spread throughout the nucleus.
12
Q
What occurs in G1of interphase ?
A
G1 or gap 1:
first stage and immediately follows mitosis, during this phase the cells will double in size & RNA,proteins, cell membrane, ribosomes and other organelles in the cytoplasm are synthesized. The cell components that are lost during the previous cell division are replaced. Chromosomes are unduplicated one molecule of DNA -You will see the chromatids again they will open up and become unpaired.
13
Q
How does the cell cycle prevent defective cells from going though mitosis and diving?
A
There are checkpoints in the cell cycle to prevent a defective cell from going though mitosis and dividing
G1 ensure readiness for DNA synthesis
G2 determines if cell is ready to enter ,mitosis and divide
** if the damage to a cell is so severe that the cell cannon be repaired the cell will self-destruct by apoptosis= cell suicide *
14
Q
what is the first phase of cell cycle? Include descriptions time frame and phases.
A
Interphase, Is the first & longest phase of the cell cycle, it is a non division phase where the cells will bulk but to get ready for division. Lasts about 18-24 hours. At the beginning of interphase the cell has just finished mitosis- mitosis is resulting in two identical daughter cells. These daughter cells will undergo growth and synthesis that will take place during the 3 phase of interphase 1. G1 or gap1 2. S or Synthesis 3. G2 or gap 2
15
Q
What happens if a cell escapes from the control of the cell cycle?
A
They become cancerous, and start dividing at a rate that they shouldn’t
cancer cells are your own cells that have become rebellious.
16
Q
How do cells become cancerous?
A
Cancerous cells happen when they escape the control of the cell cycle. cancer cells are your own cells that have become rebellious, they start dividing at a rate that they shouldn’t
17
Q
Explain how many chromosomes a human has
A
Human= 45 chromatids or chromosomes unpaired
OR
Human= 23 Chromosomes Paired
18
Q
Explain how many chromosomes an sperm has
A
Sperm=23 Chromatids or chromosomes unpaired
19
Q
Explain how many chromosomes an egg has.
A
Egg=23 Chromatids or chromosomes unpaired
20
Q
What is Hydrophilic:
A
Hydrophilic= water loving phosphate group “head” ends towards the outer and inner surface of the plasma membrane
21
Q
What is Hydrophobic
A
Hydrophobic = water-hating Fatty acid “tail” – are buried within the interior of the membrane
22
Q
What is the plasma membrane function:
A
The cell membrane regulates the transport of materials entering and exiting the cell. Phospholipids membrane are impermeable to water, all ions and hydrophilic small molecules
Plasma membranes contains groups of proteins some proteins allow ions to cross, some serve to attcach cells to surrounding cells and some proteins give the cell its shape or allow its shape to change.
Molecules on the plasma membrane provides cells with molecular identity – such as blood type and organ transplant compatibility
Some gentic disorders are associated with plasma membrane abnormalities.
23
Q
What is a plasma membrane:
A
The cell membrane, also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment. The plasma membrane is composed of a bilayer (two layers) of phospholipid. Hydrophobic = water-hating Fatty acid “tail” – are buried within the interior of the membrane Hydrophilic= water loving phosphate group “head” ends towards the outer and inner surface of the plasma membrane
24
Q
What is Gestation?
A
It is the period between conception and birth
25
Karyogram:
is the study of a whole set of chromosomes arranged in pairs by size and position of centromere.
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Apoptosis:
Cell suicide, very clean process and it does not damage surrounding cells
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Heterozygous/heterologous
Carrying two different alleles for one or more genes
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Homozygous/Homologous
Carrying identical alleles for one or more gene
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Karyotype
The general appearance of somatic chromosomes, as far as what they look like not a phenotype. The chromosomes laid out and what the chromosome looks like.
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Phenotype:
The expression of the allele combination present in a gene, how you are going to look. the phenotype is the set of observable characteristics or traits of an organism. Eye, hair ect
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Genotype:
the genetic makeup of an organism, describes the alleles present in a gene the fundamental characteristics of an organism intern of hereditary factors
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Diploid:
Where each chromatid or chromosome unpaired is represented twice in a chromosome paired. One from each parent. Humans are always diploid 46 chromatids/chromosomes unpaired OR 23 Paired chromsomes
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Haploid
One full set of chromatids or Chromosomes unpaired occurring in a mature germ cell OR half the number of chromosomes Paired. 23 chromatids or chromosomes unpaired
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Ploidy:
Number of sets of chromosomes in a biological cell.
35
What is a mutation?
Point and frame shift mutations
Different types of Point mutations and how they can occur
36
What is the difference between transcription and translation?
Outcome of transcription & translation
37
What are codons?
a codon is each group of Three nucleotides is called a codon and specifies an amino acid
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What is translation?
* is like following the copied recipe to make a dish.
* It happens in the cell's ribosomes, which are like molecular machines.
* The mRNA attaches to the ribosome.
* Transfer RNA (tRNA) molecules bring amino acids to the ribosome, matching them to the mRNA's instructions.
* The amino acids are linked together to form a protein chain, following the instructions on the mRNA.
* Once the protein is finished, it folds into its proper shape and goes to do its job in the cell.
* So, in simple terms, transcription is the process of copying DNA into mRNA, and translation is the process of reading that mRNA to build a protein. It's like going from a recipe (DNA) to a copy of that recipe (mRNA) and then following the copy to make the dish (protein).
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What is transcription?
* Transcription is like making a copy of a recipe.
* It happens in the cell's nucleus.
* The DNA unwinds, and an enzyme called RNA polymerase reads one side of the DNA.
* RNA polymerase then builds a molecule called messenger RNA (mRNA) by matching RNA bases to the DNA bases.
* The mRNA is a copy of the recipe (gene) needed to make a protein.
* Once the mRNA is made, it leaves the nucleus and goes to the ribosomes
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What are amino acids?
Amino acids are molecules that combine to form proteins. Amino acids and proteins are the building blocks of life.
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Meiosis- only germ cells
Meiosis is only for germ cells. It is a two cell divisions cycle. The chromosomes undergo one stage of replication and two stages of division. it consists of Meiosis I & Meiosis II,
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Mitosis
Mitosis is the second phase of the cell cycle. Mitosis is the division phase of the cell cycle.
divsion of the nucleus
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3 phases of interphase
G1 or gap 1:
first stage and immediately follows mitosis, during this phase the cells will double in size & RNA,proteins, cell membrane, ribosomes and other organelles in the cytoplasm are synthesized. The cell components that are lost during the previous cell division are replaced. Chromosomes are unduplicated one molecule of DNA -You will see the chromatids again they will open up and become unpaired.
S or Synthesis:
Duplication this is when the two identical daughter DNA molecules of each chromsomes occurs. DNA is replicated and doubles. Chromosomes are very long and spread throughout the nucleus.
G2 or gap 2
It is the phase following DNA duplication and the last phase before mitosis. A second period of cellular growth occurs, mitochondria divide and precursors of spindle fibers are formed. By the end of G2 the cell is ready to divided (mitosis)
44
Interphase
Is the first & longest phase of the cell cycle, it is a non division phase where the cells will bulk but to get ready for division. Lasts about 18-24 hours.
At the beginning of interphase the cell has just finished mitosis- mitosis is resulting in two identical daughter cells. These daughter cells will undergo growth and synthesis that will take place during the 3 phase of interphase
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The cell cycle of somatic cells
The cell cycle of somatic cells consists of three phases.
Interphase is the longest phase & is a period of non-division. It is bulking up in order to get ready for division. 18-24 hours
Mitosis Division of the nucleus lasts about 1-2 hours
Cytokinesis is the Division of the cytoplasm
Some cells like bone marrow cells pass though the cell cycle continually to form red blood cells (RBCs)
Some cells enter a resting or G0 phase
This state can be temporary and most cells in G0 can re enter the cell cycle if the conditions change.
Other cells like cochlear hair cells & neurons that have reached an end stage of development will stay permanently in G0 and will no longer divide.
When cells escape from the control of the cell cycle they become cancerous- cancer cells are your own cells that have become rebellious, they start dividing at a rate that they shouldn’t
46
Chromosomes disorders
Down syndrome= is a duplicate of chromosome 21 AKA Trisomy 21
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Chromatin/chromosomes
A single chromosome is called a chromatin
Chromosomes The complex of DNA and proteins that make up a chromosome is called chromatin.
Chromatin or organized into chromsomes
One chromosomes is two chromatids
One chromosomes is two chromatids that’s are connected at the Centromere to create an “X” formation.
When they are connected at the centromere there is a short and long arm. (TOP)Short arm=P (Bottom) Long arm=Q
Two Chromatids joined by a centromere are called sister chromatids.
Each Human has 45 chromatids or chromosomes unpaired OR 23 Chromosomes Paired.
this is made up of 22 autosomes pairs & one pair of sex chromosome (XX or XY)
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Nucleus:
Contains our DNA
Largest most prominent of the membrane-bounded organelles which characterize eukaryotic cells
Responsible for growth and cell reproduction
Double membrane that allows direct communication between the nucleus and cytoplasm
Contains dense regions called nucleoli that synthesize ribosomes
Dark strands and clumps of chrimatin (chromsomes) are seen thought the nucles, this is where the DNA is located.
Contains DNA organized into genes that determines shape, structure and range of functions carried out by the cell.
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Mitochondria:
Largest Organelle surrounded by 2 phospholipid bilayer membranes
Produces ATP energy source of cell “power house of the cell”
Ancestors of bacteria : Mitochondria are believed to originate as bacteria that took up residence in eukaryotic cells and over time became welcome collaborators. Over time many of the bacterial genes migrated to cell nucleus and were incorporated in the cells nuclear genome. Mitochondria still contains small genomes that encode essential proteins revealing their bacterial origins
50
Lysosomes:
Membrane enclosed sacs that contain digestive enzymes
They break down or recycle worn out or obsolete cell parts
51
Golgi Apparatus
Flattened membrane sacs that receive proteins from the ER
52
Ribosomes
Found in the endoplasmic reticulum and free in the cytoplasm
Made up of ribonucleic acid RNA and proteins
Primary site of biological protein synthesis
Ribosomes link amino acids together in the order specified by messenger RNA (mRNA) molecules
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Endoplasmic Reticulum:
Smooth ER: no ribosomes and it functions in lipid synthesis
Rough ER: it is associated with ribosomes & it functions in the synthesis and processing of proteins.
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Organelles
in human cells except red cells, contains extensive internal membranes that enclose specific subcellular compartment. Each organelels have there own set of proteins. Organelles are strcutres within the cytoplasm and include the endoplamic reticulum smooth and rough.
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Cytoplasm
The plasma membrane encloses the cytoplasm, a comlex mixture of molecules and structural components. Within the cytoplasm is the cytoskeleton. cytoskeleton provides shape, anchors cellular structures and organization
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Know the primary structures and their functions within human cells
Plasma or cell membrane:
The cell membrane, also called the plasma membrane, is found in all cells and separates the interior of the cell from the outside environment.
The cell membrane regulates the transport of materials entering and exiting the cell.
The plasma membrane is composed of a bilayer (two layers) of phospholipid.
Hydrophobic = water-hating Fatty acid “tail” – are buried within the interior of the membrane
Hydrophilic= water loving phosphate group “head” ends towards the outer and inner surface of the plasma membrane
Phospholipids membrane are impermeable to water, all ions and hydrophilic small molecules
Plasma membranes contains groups of proteins some proteins allow ions to cross, some serve to attcach cells to surrounding cells and some proteins give the cell its shape or allow its shape to change.
Molecules on the plasma membrane provides cells with molecular identity – such as blood type and organ transplant compatibility
57
What is cell signaling?
Cell signaling is the transfer of information from one cell to another. Cells signal each other by direct contact with each other OR by the release of substance such as hormones or neurotransmitters for cell growth and work normally
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Eukaryotic cells:
These cells possess both plasma membrane and nuclear membrane along with other organelles. Nucleus contains DNA Human cells.
Each cell can function on its own as a single unit
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Prokaryotic cells
Have a plasma membrane/cell wall but do not have membrane-bound nucleus or other membrane organelles. Prokaryotic DNA is found in a coiled loop. Unicellular cells= most bacteria are prokaryotes
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What are the two main cell types?
Prokaryotic and Eukaryotic cells
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Nonsyndromic conditions:
only one system is affected
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Syndronic conditons
more then one system is affected
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Germ Cells
Egg & sperm- are the only cells that are capable of making new life
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Somatic cells
Everything except sex cells. Are cells that differentiate into tissues and organs in t he body
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When do the Pharyngeal/brachial arches form?
22 days post conception
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What develops from the 1st & 2nd arch?
1st&2nd arch are critical to the development of face, outer ear and middle ear
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What forms the external and middle ear?
Pharyngeal arches, pouches, cleft and the neural crest cells form 1&2
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What does each arch have?
Has its own nevre cartilage and artery.
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What Develops from Pharyngeal cleft 1&2?
When does the formation of the EAC begin and end?
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What happens if a cervical sinus doesn’t disappear?
It forms a lateral or bronchial cysts or fistula.
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What does the 2nd, 3rd and 4th cleft form?
The Cervical sinus, the cervical sinus will eventually disappear
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What does the Branchial Membrane form?
Tympanic membrane
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What is the Tympanic Cavity derived from?
Endoderm.
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What is the External ear derived from?
Ectoderm.
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How many layers does your TM have?
Three. Outer, middle and inner.
Its outer layer is formed by the ectodermal meatal plug of the EAC
Its middle layer is mesoderm derived from neural crest cells
The inner layer is endoderm derived, the epithelial lining of the tympanic cavity.
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what is the Tubotympanic recess derived from?
Endoderm
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What forms the ME?
The ME is formed by the tubotympanic recess, which is an extension of the First Pharyngeal pouch.
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What is the time frame of the ME formation?
The middle ear formation begins at about week 8 and ends at about week 21.
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What is derived of the second arch?
Stapedius muscle
Stapes – derived from the cartilage of the 2nd arch
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What is derived of the first arch?
Tensor tympani muscle
Malleus & Incus – derived from the cartilage of the 1st arch
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When does the pinna complete formation ?
Pinna formation is completed at week 30
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What happens at week 7 for pinna?
By the 7th week the hillock enlarge and fuse to form. The auricle or pinna.
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Clefts and Cysts location
Clefts are outside of the branchial arches and the cysts/sacks are on the inside.
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What happens at week 5 for pinna?
During week 5 the hillocks are arise on the branchial clefts
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Where are the auricular hillocks located?
The hillocks are located between the 1st and 2nd Pharyngeal arches, three on each side of the ear canal
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What does the pinna develop from?
six mesenchymal projections, called auricular hillocks, produced by the migration of neural crest cells
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Why do these 1st and 2nd arch syndromes typically have conductive HL?
Because the 1st and 2nd arches are responsible for the development of the middle and outer ear.
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Stickler Syndrome:
Underdevelopment of the middle of the face and small lower jaw, eye abnormalities, retinal detachment. Conductive HL, joint problems are also reported.
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Pierre robins syndrome:
Smaller lower jaw, tongue is large and placed further back, cleft palate. Typically connected to otitis media & conductive HL
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Teacher Collins syndrome:
First arch syndrome small lower jaw, large mouth and abnormal ear (peanut ear)
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What are some 1st and 2nd syndromes?
Teacher Collins syndrome: First arch syndrome small lower jaw, large mouth and abnormal ear (peanut ear)
Pierre robins syndrome: Smaller lower jaw, tongue is large and placed further back, cleft palate. Typically connected to otitis media & conductive HL
Stickler Syndrome: Underdevelopment of the middle of the face and small lower jaw, eye abnormalities, retinal detachment. Conductive HL, joint problems are also reported.
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What is a 1st & 2nd Pharyngeal arch syndrome?
Malformation from the 1st and 2nd arches, pouches and clefts
It needs to have at least 2 of the following features.
The major features of these syndromes include …..
-Cleft lip or without cleft palate
-Micrognathia= small or undersized lower jaw (not everyone who has a small jaw has this but when you see it with these other disorders.
-External Audtiory Canal- Abnormalities/atresia with or without pinna abnormalities. EX atresia=absence of a canal
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4th&6th arches (fused)
Boney: Laryngeal Cartilages
Muscle: Cricothyroid muscle, levator palatine muscle, pharyngeal constructors, intrinsic muscle of the larynx.
Nerve: Vagus Nerve (X)
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3rd arch
Boney: Greater horn of the hyoid bone, lower portion of body of hyoid bone
Muscle: Stylopharyngeus muscle
Nerve: Glossopharyngeal Nerve (IX)
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2nd arch
Boney: Stapes, styloid process, lesser horn of the hyoid bone, an dupper portion of body of the hyoid bone.
Muscle: Muscles of facial expression, posterior belly of digastric stylohyoid, stapedius
Nerve: Facial nerve (VII)
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1st arch
Boney: malleus and incus Maxillary bone, Zygomatic bone, temporal bone, mandible,
Muscle: Muscle of mastication, Mylohyoid muscle, anterior bellu or digastric, tensor tympani, tensor palatine muscle.
Nerve: Trigeminal nerve (V)
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Why do these 1st and 2nd arch syndromes typically have conductive HL?
Because the 1st and 2nd arches are responsible for the development of the middle and outer ear.
Summary
Most of the head and neck develops from the Pharyngeal arches
Each arch has ectoderm on the outside, a mesodermal core and an endoderm on the inside.
The mesodermal core develops a cartilage/boney component after being invaded by neural crest cells, a cranial nerve co mponent and a vascular component. That’s why it si important for each arch to have it own artery, nerve and cartilage.
Externally there is a pharyngeal cleft between each pair of pharyngeal arches..
The clefts go though a sequence of development to then dissaper when done however if the cleft doesn’t go away it can form a cervical or branchial fistual or cysts
Internally There is pharyngeal pouch/cysts between each pair of pharyngeal arches – these endodermal pouches devlope the TM, tonsils ect.
Pharyngeal arches are developing several prominennces are contributing to the development of the face.
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Syndrome examples:
Teacher Collins syndrome: First arch syndrome small lower jaw, large mouth and abnormal ear (peanut ear)
Pierre robins syndrome: Smaller lower jaw, tongue is large and placed further back, cleft palate. Typically connected to otitis media & conductive HL
Stickler Syndrome: Underdevelopment of the middle of the face and small lower jaw, eye abnormalities, retinal detachment. Conductive HL, joint problems are also reported.
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1st & 2nd Pharyngeal arch syndromes
Syndrome= is when you have more that one structure involved at least 2.
Malformation from the 1st and 2nd arches, pouches and clefts
The major features of these syndromes include …..
-Cleft lip or without cleft palate
-Micrognathia= small or undersized lower jaw (not everyone who has a small jaw has this but when you see it with these other disorders.
-External Audtiory Canal- Abnormalities/atresia with or without pinna abnormalities. EX atresia=absence of a canal
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Vestibular system
Week 6- semicircular canal appear as flattened out-pockets of the urtocle portion of the otic vesicle
Central portion out-pocketing’s disappears and gives rise to the three semicircular canals
one end of each canal dilates to form the crus ampullae, containing the sensory cells for equilibrium and balance
the semicircular canals utricle and saccule are filled with endolymph
the three canals are covered by bone
fluid between the outer boney covering and semicircular canal is the perilymph
the three semicircular canals are sensititive to angular motion or rotation.
The maculae in the utricle and saccule are very sensitive to linear acceleration
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The epithelial cells of the cohlear duct form two ridges inner and outer ridge.
Inner ridge= form spiral limbus
Outer ridge= gives rise to 3 rows of outer hair cells and 1 row of inner hair cells
At the end of the 5th month the cochlea is developed and functional
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Week 6
semicircular canal appear as flattened out-pockets of the urtocle portion of the otic vesicle
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Week 7 to 8
o 8 the cochlea exits the cell cycle and sensory epithelia begins to develop.
The epithelial cells of the cohlear duct form two ridges inner and outer ridge.
Inner ridge= form spiral limbus
Outer ridge= gives rise to 3 rows of outer hair cells and 1 row of inner hair cells
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Week 10
the cartilage surrounding the cochlear duct undergoes vacuolization (opening) and forms two perilymphatic space Scalia vestibuli and Scalia tympani
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9th week
of gestation the mesenchyme surrounding the inner ear form the otic capsule
Otic capsule will become the petrous portion of the temporal bone and called the bony labyrinth
The auditory nerve which develops from the neural crest cells piercing the otic capsule into two main divisions vestibular system & cochlea
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week 8
it has completed its 2 3/4th turn that’s makes up the cochlea & and it remains connected to the saccule via the ductus reuniens
The uticle and saccue communicate though the utricuosaccular duct
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week 6
development of the saccule forms a tubular shaped out-pocket in its lower pole that is the beginning stages of the cochlear duct, penetrating the surrounding connective tissue (mesenchyme) to form the cochlea
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week 4, 28 days
the otic vesicle splits from the surface ectoderm, diving into a ventral and dorsal portion.
The Ventral portion forms the
Saccule (part of the vestibular system)
Cochlear duct (future Scala media of the organ of corti)
The Dorsal portion forms the
Future utricle and semicircular canal (both parts of the vestibular system)
Endolymphatic duct
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The Inner ear
The inner ear develops form the otic placode, first indication of inner ear development is 22day
Labyrinth develops into the cochlea and vestibular system
The primitive brains consisting of Prosencephalon/forebrain, mesenchephalon/midbrain, rhombencephalon/hindbrain- will subdivided into the pons and medulla oblengata
Ectodermal thicking on either side of the rhombencephalon/hindbrain will devlop into the medulla called the otic placode.
The otic placode develops into the inner ear
At about 22days the ectoderm becomes the epithelium of the inner ear.
At this point hearing and balance mechanism are both present in the inner ear.
The otic placode invaginates (forming a cavity/canal) moves deeper and deeper towards the base of the skull. To form the otic cup/otic pit and
ultimately into the primitive auditory/otic vesicle located dorsal to the 2nd pharyngeal cleft
Otic induction is the time from the ectodermal thickening adjacent on day 22 to 23 till complete invagination of the otic vesicle on day 26 (4 day process)
-A Number of genes are implicated in the process of otic induction, and the disruption of which can result in inner ear abnormalities and Hearing loss
The otic placode & invagination is parallel with the Neural crest cells. These migrating neural cells aid in the formation of the External ear (Tympanic membrane) , middle(ossicles) and inner ear( optic capsule & sensory neurons)
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The Auricle or Pinna
The pinna develops from six mesenchymal projections, called auricular hillocks, produced by the migration of neural crest cells – FUN FACT: no 2 pinnas are alike
The hillocks are located between the 1st and 2nd Pharyngeal arches, three on each side of the ear canal
During week 5 the hillocks are arise on the branchial clefts
Clefts are outside of the branchial arches and the cysts/sacks are on the inside.
By the 7th week the hillock enlarge and fuse to form. The auricle or pinna.
Pinna formation is completed at week 30
All of the ear structures all develop from the pharyngeal arches.
From Ventral to dorsal the 3 projections on the 1st pharyngeal cleft is Tragus, helix and Cymba concha
From Ventral to dorsal the 3 projections on the 2nd pharyngeal cleft is Antitragus, antihelix and concha
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Second Pharyngeal Arch
Stapedius muscle
Stapes – derived from the cartilage of the 2nd arch
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First Pharyngeal arch
Tensor tympani muscle
Malleus & Incus – derived from the cartilage of the 1st arch
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The Ossicles are formed by the Pharyngeal arches 1&2
The three ME ossicles develop independently from the tubotympanic recess with neural cell contribution.
The ossicles are derived from the 1st &2nd Pharyngeal arches
The ossicles are made up of cartilage embedded in Mesenchyme adjacent to the tympanic cavity.
During the 8th month of gestation, the Tympanic cavity envelops the ossicles. Meaning that at first the ossicles are separate from the tympanic cavity (TC) and then the TC goes around the ossicles making them apart of the TC.
Ossicles form a lever system- They diminish the force of sound wave in ME and increase the force of sound wave on the inner ear.
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The tubotympanic recess is
derived from the endoderm
Motile cilia In the ME clears mucus and pathogens out of the ME cavity and into the throat though the Eustachian tube. Neural crest cells are believed to play a role in the development of these cilia. When the cilia breaks down ME infection can arise.
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The middle ear formation
begins at about week 8 and ends at about week 21.
The ME is formed by the tubotympanic recess, which is an extension of the First Pharyngeal pouch.
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The Pharyngeal Pouches forms the
Tympanic Cavity & Eustachian tube
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The Tympanic Membrane or Ear Drum is formed
is formed from the Branchial Membranes.
The TM marks the boundary between outer and middle ear
It is formed at the border of the meatal plug of the external ear derived from the ectoderm and the Tympanic cavity derived from the endoderm.
The TM is made of three layers.
Its outer layer is formed by the ectodermal meatal plug of the EAC
Its middle layer is mesoderm derived from neural crest cells
The inner layer is endoderm derived, the epithelial lining of the tympanic cavity.
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2nd,3rd and 4th cleft form the
form the cervical sinus that will later disappear. If the cervical sinus does not disappear this forms the lateral or bronchial cysts or fistula.
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External Auditory Canal (EAC) is formed
from the 1st & 2nd Pharyngeal Cleft
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Pharyngeal or Branchial Arches
Major features of the ears, face and palate emerge during the embryonic period primarily during week 4 – week 8
Initially you have 1-6 Pharyngeal arches (cranial to caudal sequence)
Arch 5 disappears and 4 though 6 fuse together forming one arch. Resulting in a total of 4 arches.
The 1st and 2nd arch are critical for the development of the face, outer and middle ear
Mesoderm of the arches develops into the Facial and auditory muscles.
The five remaining Pharyngeal arches are separated externally by a cleft and internally by pouches.
1 & 2 arches, their pouches, cleft and neural crest cells form the external and middle ear.
The middle and external ear are just 2 out of many structures that develop from 1&2 arches, pouches, cleft and neural crest cells.
Multitude of syndromes that include abnormalities of the ear and facial defects come from 1&2
Each arch has its own nerve, cartilage and artery.
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Characteristics of the fetal period:
Relative head size decreases
Completion of the development of the organ systems
Hair appears on the head and body
Fetus gains weight from the development of the subcutaneous fat
Fetus is getting ready for external life.
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The fetal period is from
week 9 - birth
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The fetal period is
from week 9 - birth
Characterized by maturation of tissues, organs and growth of the body.
Fetus looks more human
Few if any physical malformations arise during this time as a result of exposure to teratogens because the major organ systems have been established.
Exposure to teratogens may still interfere with growth and normal function such as Autism, ADHD, dyslexia ,language delays ect.
Because cell death in CNS may result in postnatal behavioral abnormalities
Many developmental disorders are believed to occur during this period such as Central Auditory Processing disorders, learning disability & language delays.
No external abnormalities they will appear completely normal. (autism, adhd)
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Other Organ Systems
The primitive gust develops at about week 4
Foregut, midgut & hindgut
The urinary system begins early in the embryonic period
Kidneys appear at about week 4
And start Producing urine at about week 11
The Gender of the fetus is determined at fertilization.
Gonads (testes or ovaries) begin developing at about week 7
External genitalia are not distinct until the fetal period; ultrasound determination of gender is between week 18-22
Who determines gender? A: father
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The primitive gust develops at about
week 4
Foregut, midgut & hindgut
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The urinary system begins early in the embryonic period
Kidneys appear at about week 4
And start Producing urine at about week 11
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The Gender of the fetus is determined at fertilization.
Gonads (testes or ovaries) begin developing at about week 7
External genitalia are not distinct until the fetal period; ultrasound determination of gender is between week 18-22
Who determines gender? A: father
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Respiratory System
Development Begins at week 3
At about week 4 there is a laryngotracheal tube which is the precursor to the trachea and larynx
The primitive pharynx is also present and must separate from the laryngotracheal tube
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Cardiovascular System
Development begin at week 3 of gestation
The Primitive heart divides into two ventricles at week 4 Approx
By week 7 a septum communication between the two chambers is closed off
Week 4=2 ventricles week 7= two chambers are closed off
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Neural Crest Cells
Is a band of of Neuroectodermal cells that lie Dorsolateral (back side and outer area,edges) to the developing spinal cord (in the neural tube)
In the neural tube they separate into clusters of cells that develop into a variety of tissues, inducing spinal and autonomic ganglia, connective tissue around the brain and spinal cord.
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Anencephaly
*More severe then spinal bifida but anencephaly is very rare. This is not compatible with life. This is a condition where the portion of the neural tube that will become the cerebrum does not close. The baby will be born without the front part of the brain (forebrain) & thinking/coordinating part of the brain cerebrum. & the remaining parts of the brain are often not covered by bone or skin
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Arnold-Chiari II or Chiari type II Malformation
It can co-exist with an encephalocele or spina bifida & type 2 is most common . The cerebellum & brainstem extend further into the foramen magnum than normal and also into the upper spinal cord. Normal flow of fluid of the brain can be obstructed causing hydrocephalus an excess of CSF within the brain.
Anencephaly
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Chiari Malformation (CM)
May develop when part of the skull is smaller then normal or misshapen, which forces the cerebellum to be pushed down into the foramen magnum and upper spinal canal. This causes pressure of the on the cerebellum and brain stem that may affect functions controlled by these areas and block the flow of cerebrospinal fluid. This can cause hydrocephalus (based on the severity)
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Myelomeningocele
Is the most significant & common encephalocele and leads to disability in most affected induvials. The terms spina bifida and myelomeningocele are usually used interchangeably
Location: lower back
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Encephalocele
It is a result of when other parts of the brain remain unfused.
Location: Most commonly this malformation is located in the lumar and sacaral areas Lower back.
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Spina Bifida in combination with Dermoid Cyst
This is the fluid filled sac that is surrounding the spinal cord.
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Spinal Bifida = Split spine (latin)
Spina Bidifa means the Spine didn’t join, incomplete closure of neural tube & is one of the most common birth defects of about 1in every 1,000 births
When some vertebrae overlying the spinal cord are not fully formed and remains unfused and open. – If the opening is large enough a portion of the spinal cord will protrude through the opening in the bones. There may or may not be a fluid filled sac surrounding the spinal cord. It can be surgically closed after birth, but usually does not restore normal function to affected parts of the spinal cord. So if it caused paralysis to the left limb when fixed you may not restore that function because it never developed properly/fully
Cause: Spina Bifida is believed to caused by a combination of genetic and environmental factors. After having one child with spina bifida risk for a second child being affected increase by approximately 4% However this can be decreased by approximately 70% when the mother starts taking folic acid supplements early in pregnancy. Environment plays a bigger role then genetics.
Location: Most commonly lower back. It can be in upper back or neck but is extremely rare.
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Neural Tube
- Is A tube formed by the closure of ectodermal tissue in the early vertebrate embryo
- It Later develops into the brain, spinal cord nerves and ganglia \
Incomplete development of the neural tube results in neural tube defects can causes defects such as
Spina Bifida
Spina Bifida in combination with Dermoid Cyst
Encephalocele
Chiari Malformation
Arnold-Chiari II or Chiari type II Malformation
Anencephaly
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Dermoid Cyst
Similar to spina bifida can even Look the same as Spina bifida but it is not the same. You would need to do more tests to be able to differentiate the two.
A dermoid cyst is a benign tumor a remnant of the primitive streak and contains all three germ layers. And spina bifida is an incomplete closure neural tube= not the same
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The primitive brain consists of ….
Prosencephalon becomes the Forebrain
Mesencephalon becomes the Midbrain
Rhombencephalon becomes the Hindbrain
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The Peripheral nervous system
(PNS) develops from Neural Crest Cells
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The central nervous system
(CNS) develops from the Neural tube
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Nervous System
Begins development by week 3
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What is Organogenesis?
Organogenesis- Organ Development
Organogenesis is the process where the Ectoderm, Mesoderm and Endoderm develop into the internal organs of the organism
Cells of each germ layer proliferate, migrate, reaggregate and differentiate into various tissues that form the organs
Cells go where they are supposed to go and they start to develop into what they are supposed to be.
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Embryonic
Embryonic Period last approximately from 3rd week to till the end of the 8th week of gestation
All major organ systems begin and undergo major development during the embryonic period.
The Embryonic period is critical for development
Which means exposure to teratogens during this period can result in either death of the embryo or major congenital abnormalities affecting multi organ system (since they are developing during this time)
Depending on time of exposure to the teratogens is what determines which organ/organs systems are affected. – However some teratogens only/specifically affect certain organs/structures.
At the end of the Embryonic period about week 8 the embryo is the size of a jellybean.
Visible external features of the embryonic period at this point such as
The head makes up about 50% of the embryo’s length
Facial features and ears are clearly distinguishable
Ears are low set
Future eyes are visable
Formation of upper and lower limbs are visible
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What develops from the Endoderm?
GI tract
The Gastrointestinal system is the main organ system that develops from this germ layer.
The epithelial lining of the respiratory tract
The epithelial lining of the lymphatic cavity and Eustachian tube
The Parenchymal cells of the thyroid and parathyroids, liver and pancreas.
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What develops from the Mesoderm?
Supporting tissue such as cartilage and bone
Dermis
Striated and smooth muscles
Blood and lymph Cells
Walls of the heart, blood and lymph vessel
Kidney, Gonads (Reproductive Organs), and corresponding ducts
Spleen
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What develops from the Ectoderm?
Central Nervous System (CNS)
Peripheral Nervous System (PNS)
Schwann cell & Meninges
Sensory Epithelium of the ear, nose and eye
Lens of the eye
Subcutaneous Glands (underneath the skin) and Pituitary Glands
Bones and connective tissue of craniofacial structures
Epidermis (thinnest and outermost skin layer) as well as hair and nails
Enamel of the teeth
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Development of the germ cells and what develops from each of the three germ layers
What gives rise to the three primary germ layers?
The epiblast gives rise to ectoderm endoderm and the mesoderm
Epiblast becomes the ectoderm and mesoderm
Hypoblast becomes the endoderm
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What is gastrulation?
Gastrulation is approximately a 2-week process occurring from Week 2 – Week 4.
Gastrulation begin with the formation of the primitive streak.
A new cell layer starts to develop between the epiblast and hypoblast
Cells of the epiblast migrate towards the primitive streak
At the streak they become flask shaped, detach from the epiblast and slip/fold underneath which is also known as Invagination.
Once the cells have invaginated, some displace the hypoblast and create the endoderm.
Some cells lies between the epiblast and newly formed endoderm to form the Mesoderm.
Cells remaining in the epiblast from the ectoderm.
By the end of the 3rd week the embryo becomes a trilaminar disk.
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what is the purpose of mitosis?
Mitosis is important to allow multicellular organisms to grow and repair damaged tissues
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what is Mitosis?
Mitosis is the second phase of the cell cycle. Mitosis is the division phase of the cell cycle.
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what are the 4 phases of mitosis?
Prophase
Metaphase
Anaphase
Telophase
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What occurs in prophase?
The chromosomes coil, thicken, shorten and begin to become recognizable.
The nucleolus fades and chromatin (replicated DNA and associated proteins) condense into chromosomes.
at the end each replicated chromosomes is made of two sister chromatids with identical genetic information joined at the centromere.
centrioles duplicate at the start of mitosis and each pair moves apart migrating to opposite poles of the dividing cell.
from the subunits a bridge of microtubules called spindles apparatus forms between the two centrioles as they move apart
Once centrioles reach opposite ends of the cell they extend microtubules in all directions (the shape of the microtubules are called aster)
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what happens in Metaphase
Begins with the complete disappearance of the nuclear membrane
Chromosomes are free in the cytoplasm
contains sister chromatids attached at centromere “X” shape
Chromosomes move to the middle of the cell wall where the fully formed spindle fibers attach to the centromeres
tension is applied b aligns all chromosomes in one place at the center of the cell
there is 46 centromeres attached to sister chromatids (double then somatic cells)
Chromosomes are in their most tightly condensed form
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What happens during anaphase?
the Attachments between the two sister chromatids break
Spindle fibers shorten, the daughter chromosomes are pulled apart and begin moving to opposite cell poles
each chromatid is considered a separate chromosome
At the end of anaphase a complete set of chromosomes is found at each end of the cell
*** anaphase is the shortest but most crucial stage of mitosis because it ensures that each daughter cell receives a completes identical set of 46 chromosomes ****
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what happens during telophase?
The daughter chromosomes arrive at the poles and the spindle fibers that pulled them apart disappear
membrane buds from the endoplasmic reticulum form a new nucleus membrane
inside the new nucleus the chromosomes uncoil, length and form threads and clumps of chromatin
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What happens during Cytokinesis?
Last phase of the cell cycle
Division of the cytoplasm takes place during this phase
Begins with the formation of cleavage or cell furrow and then eventually divides the cell into two daughter cells
Microtubules then reorganize into a new cytoskeleton for the return of the cell to interphase
Each daughter cell receives one-half of the (92) chromatids in order to maintain the same number of chromosomes as the mother cell.
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when is meiosis occurring?
During the embryological period
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what is the purpose of meiosis?
Meiosis prepares the organism for fertilization.
to provide genetic variability through the process of cross over (meiosis I and prophase I)
&
to provide each germ cell with the correct ½ or haploid number of chromosomes. (meiosis II)
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How many daughter cells are produced at the end of mitosis?
2 identical daughter cells
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How many daughter cells are produced at the end of meiosis?
4 non-identical daughter cells
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Each daughter cell receives how many chromosomes in mitosis?
46 chromosomes unpaired/ chromatids
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Each daughter cell receives how many chromosomes in meiosis?
23 chromosomes unpaired/chromatids
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What Is Gametogenesis?
Gametogenesis is put into action by the cell division of meiosis 1&2. during this
each normal ovum/egg contains an X chromosome
and ½ the number for sperm contains an X and the other ½ contains a Y
resulting in Fertilization producing a 44 XX from (female zygote) & 44XY from (male zygote)
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what are the two characteristics features of meiosis (different from mitosis)
pairing aka bivalents: Chromosomes don't pair because they are XXor XY
cross over: swapping of genetic information by the chromosomes wrapping about the homologues
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what are the phases of meiosis?
Meiosis I
Prophase I- when characteristics 1& 2 occur
Metaphase I
Anaphase I
Telophase I
Cytokinesis I
Meiosis II
Prophase II
Metaphase II
Anaphase II
Telophase II
Cytokinesis II
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how many cell divisions do you go though in meiosis & why?
because a germ cell (sperm and egg) have 23 chromatids. and since we start off with 92. to get the correct number you need to divide twice. 92/2=46 46/2=23
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What is Meiosis?
Meiosis is only for germ cells. It is a two cell divisions cycle. The chromosomes undergo one stage of replication and two stages of division. it consists of Meiosis I & Meiosis II,
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When do chromosomal abnormalities originate?
they originate during the meiotic division and can involve any chromosome
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What is the process of Spermatogonia?
Primary Spermatocytes enter a 22 day prophase
Secondary spermatozoa begin the second meiotic division and form spermatids containing haploid (the correct number of chromosomes)
64day is required for a spermatogonium to form a spermatid
Spermiogenesis begins. changes that occurs is
condensation of the nucleus and shedding of the cytoplasm
now that the cytoplasm is shed the sperm cannot contribute mitochondria to the fertilized egg.
in result means that mitochondrial disorders are transmitted to offspring though mother only.
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what is the process of oogenesis?
Oogenesis is how the egg is going to develop.
at about week 3 primordial germ cells appear in the wall of the yolk sac
They then migrate to the gonads for the embryo around week 4 or 5
Female embryo becomes oogonia
these cells continues to divide by mitosis (because there is no meiosis at this point)
by the end of 3rd month you have some primary oogonia while the other continue to divide but in meiosis Primary oogonia: will become the X cells
immediately after the primary oocytes replicate their DNA and enter prophase 1 for the first meiotic division
The oogonia will increase rapidly for the first few months.
5th months 7,000,000 germ cells will be created (maximum)
by month 7 many of them will die out leaving you with maybe 2,000,000
the remaining oocytes enter prophase of meiosis
they do not enter metaphase but instead enter diplotene (where they get frozen )
Postnatal maturation (at puberty only about 400,000 oocytes are present)
primary oocytes are frozen in diplotene until puberty where they will fished meiotic division
at puberty about 5-15 oocytes will mature with each ovarian cycle but only one typically will reach full maturity.
once the oocyte enter metaphase of meiosis 2 and spindle formation happens ovulation occurs
the second maturation division is only of the oocyte is fertilized.
If it is not the cell degenerates 24 hours post ovulation
how are mitochondrial disorders transmitted?
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how are mitochondrial disorders transmitted?
mitochondrial disorders are transmitted to offspring though mother only. because perm cannot contribute mitochondria to the fertilized egg because the cytoplasm was shed.
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Spermatogonia
Immature sperms
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Spermatozoa
mature sperms
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when does differentiation begin in spermatogenesis
puberty
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when does differentiation begin in female?
in utero at the third month of development
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How many oocytes are present at puberty
5,000
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How many oocytes are ovulated in the reproductive life of a female?
500
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What is spermatogenesis?
it is the process of how the sperm is going to develop
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What is oogenesis?
it is the process of how the egg is going to develop
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what is a chromosome made of?
DNA+genes+ histones = chromosomes
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When does mitosis occur?
during the pre embryonic, embryonic and fetal stages of somatic cells
& throughout life to repair/replenish cells
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How many genes does the Human genome project estimate?
20,000-25,000 genes
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what is a nucleotide:
is the building block to DNA & consists of deoxyribose sugar, phosphate molecule & and nitrogen base (A,G,C,T)
DNA news one base and the base is the information carriers of genetic material
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What nitrogenous bases are one ring structures?
Cytosine (C) & Thymine (T) - one ring structures
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What nitrogenous bases are two ring structures?
Adenine (A) & Guanine (G) - two ring structures
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what are the 4 nitrogenous bases in DNA
Adenine (A) & Guanine (G) - two ring structures
Cytosine (C) & Thymine (T) - one ring structures
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What does DNA stand for?
deoxyribonucleic acid
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what is DNA made up of?
repeating units of nucleotides. each nucleotide contains a deoxyribose sugar and phosphate molecule
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what are telomeres?
shoelace caps, telomeres are on each end of the chromosomes & they protect the end of chromosomes
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What is DNA?
DNA is the genetic code that determines all the characteristics of a living thing.
DNA carries genetic information it is shaped like a double helix.
Only DNA transfers heritable information from one bacterial strain to another
DNA controls the synthesis of proteins
Transfer of DNA results in the transfer of the ability to synthesize a specific gene product
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What is DNAs two primary functions?
duplicate its self
control the development of the rest of the cells in a specific manner.
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what is the sugar called in DNA and RNA?
deoxyribose -DNA
Ribose - RNA
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What is a protein?
Proteins carry out the genetic code.
Proteins are the product of your genes.
Proteins are the intermediate between the genes and the phenotype
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what is the result of protein function?
phenotypes of cells, tissues and organisms
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Because proteins are ….
proteins are products of genes. genes are made up of DNA information encoded in the dna MUST control the kinds and amounts of proteins present in cells.
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what are proteins made of?
amino acids. There are twenty essential amino acids in proteins.
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What are amino acids?
Amino acids are molecules that combine to form proteins. Amino acids and proteins are the building blocks of life.
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Does your body produce all amino acids?
no, they only produce 10 of the 20 essential amino acids
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what does every amino acid have?
Amino group (-NH2)
Carboxyl group (-COOH)
R group (R is unspecified group)
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whats is rRNA
rRNA is a structural component of ribosomes.it makes up part of the polyribosomes and is synthesized in the nucleolus. rRNA are powerful took in identifying species from sequencing data
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what is mRNA
mRNA is the template upon polypeptides are synthesized. mRNA occupies the crucial connecting link between information contained in a gene and its end result as the specific amino acid sequence of a protein. mRNA is found in the nucleus
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what is tRNA
tRNA are small molecules which in cooperation with ribosomes bring amino acids into position along the mRNA template. tRNA are used to carry out the translation from the mRNA sequence to the protein sequence
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how many types of RNA are there?
3, tRNA- Transfer RNA, rRNA-Ribosomal RNA, mRNA- Messenger RNA
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DNA & RNA differences
DNA
double- stranded
Thymine as a base
contains deoxyribose as sugar
maintains proteins encoding information
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RNA
usually single stranded
Uracil as base
contains ribose as the sugar
carries proteins decoding information
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where is DNA found ?
nucleus and mitochondria
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where is RNA found?
Cell cytoplasm particularly in association with ribosomes. ribosomes are protein synthesis that form proteins through the process of translation in the cell cytoplasm
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what are the 4 RNA bases ?
Adenine (A) & Guanine (G)
Cytosine (C) & Uracil (U)
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what are the 4 DNA bases?
Adenine (A) & Guanine (G)
Cytosine (C) & Thymine (T)
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what base is only found in DNA?
Thymine
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what base is only found in RNA?
Uracil
what base is only found in RNA?
Uracil
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What does RNA stand for?
ribonucleic acid
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what are the codons that only have one code?
Methionine-AUG (start codon)
and Trytophan
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what is a codon?
each group of Three nucleotides is called a codon and specifies an amino acid
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why is methionine important?
Methionine is the start codon. it only has one codon unlike all the others
Methionine code is= AUG
218
what is the start codon?
AUG-Methionine
219
AUG
Methionine (start codon)
220
Methionine codon?
AUG (start codon)
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What is transcription?
Transcription is the information encoded in a gene is copied into the messenger RNA mRNA
is the transfer of genetic information from DNA to RNA
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what are the three stages of transcription
initiation
elongation
termination
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RNA base parining
G &C
A & U
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End result of transcription- MRNA result
mRNA is a single stranded complementary copy of the nucleotide.
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what are the three stages of translation?
initiation
elongation
termination
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What is translation?
Translation in human and other organisms the rRNA move to the cytoplasm
In the cytoplasm the information encoded in the RNA nucleotide sequence of mRNA is converted to an amino acid sequence of a protein.
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End result of translation- Proteins result
amino acid continue to be added to the growing polypetide chain until the stop codon is reached
the stop codons do not code for amino acids and there are no tRNA molecules with anticodons for stop codons
at this point the protein synthesis
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What are codons?
You must know the start and stop codons
1 start AUG
3 are stop codons UAA, UAG and UGA
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what are the stop codons?
UAA, UAG and UGA
230
What are codons?
a codon is each group of Three nucleotides is called a codon and specifies an amino acid
231
antibiotics:
are chemical produced micro organisms and defense mechanisms against other microbes.
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what is Epigenetics:
it is the study of how behaviors and environment can cause changes that affect the way genes work- change the expression of genes but not the genotype.
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How epigenetics is different than genetics?
epigenetics charges are reversible and do not change the underlying DNA but they can change how the body read a DNA sequence. changes the phenotype not genotype
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What is a mutation?
is a permanent change in gene’s biochemical makeup; a change at the DNA level
235
Point mutations
point mutations cause the replacement of a single base nucleotide. they can occur in boht DNA &RNA there are two types of point mutations. nonsense, silent mutations, missense mutation
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what are the three types of point mutations?
nonsense, silent mutations and missense mutation
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what are nonsense mutations?
codes for a stop codon, prematurely stopping a protein translation. all nonsense mutations are bad.
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what are silent mutations?
is when it codes for the same amino acid but with the wrong or incorrect codon. but the result is the same.
EX: UUU or UUC they both = phenylalanine
239
what are missense mutation?
there are two types of missense mutations. Conservative and non-conservative
240
what is Conservative missense mutation?
results in a different amino acid but they are not problematic. as long as you get a result that is similar to the original amino acid.
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what is non- Conservative missense mutation?
Not a forgiving mutation, has a phenotypic effect. it could be lethal if it is an amino acid that do go together or it could juts result in an amino acid that the protein didn't need.
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frame shift mutation
can occur because of insertion or deletions of a single or more base pair.
it codes incorrectly since it only read 3 at a time.
original: ACG AGG ACU GCA
deletion example A CGA GGA CUG CA
insertion example : AAA CGA CGA GGA CUG CA
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Gene
genes are the physical units of heredity. genes are what passed on from generation to generation.they are the basic structural and functional unit of genetics. genes are made up of DNA. genes provide instructions to make proteins.
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Allele
is another word for gene. gene and allele are interchangable, An allele is one of a number of alternate forms of the same gene.
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Oocyte
Female germ cell
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Spermatocyte:
male germ cell
