Topic 3: Voice of the Genome Flashcards
(96 cards)
1
Q
what are the differences between eukaryotic and prokaryotic cells?
A
eukaryotic
- contains membrane-bound organelles (nucleus, mitochondria, ER)
- 80s ribosomes
prokaryotic
- no membrane-bound organelles (circular DNA instead of nucleus)
- 70s ribosomes
2
Q
name all the components of an animal cell (12)
A
- centrosome and centrioles
- lysosome
- mitochondria
-rER - sER
- nucleus
- nucleolus
- cytoplasm
- CSM
- ribosomes
- golgi apparatus
- microvilli
3
Q
what is the function of the nucleolus?
A
ribosome synthesis
4
Q
what is the function of the lysosome
A
contains digestive hydrolytic enzymes to digest invading cells or break down cell components and to break down waste materials such as worn-out organelles,
Lysosomes are used by cells of the immune system and in programmed cell death, known as apoptosis
5
Q
what is the function and structure of the cell surface membrane?
A
controls the exchange of materials
partially permeable
phospholipid bilayer
6
Q
what is the function and structure of the nucleus?
A
- contains chromatin (material that makes chromosomes)
- separated from the cytoplasm by the nuclear envelope (a double membrane with pores)
- nucleolus in the nucleus = site of ribosome production
7
Q
what is the function and structure of the mitochondria
A
- site of aerobic respiration
- surrounded by cristae (double membrane w folded inner membrane)
- matrix of mitochondria contains enzymes to produce ATP
- mitochondrial DNA and ribosomes also found in the matrix
8
Q
what is the function and structure of the ribosomes
A
site of translation in protein synthesis
- can be found as free organelles or on the rER
- each ribosome is a complex of rRNA and proteins
- 80s ribosomes = eukaryotic
- 70s ribosomes = prokaryotic, mitochondria and chloroplasts
9
Q
what is the function and structure of the rER
A
- role = to process proteins made on the ribosomes
- formed from folds of membrane continuous with the nuclear envelope
- covered in ribosomes
10
Q
what is the function and structure of the sER
A
- role = involved in the production, processing and storage of lipids, carbs and steroids
- formed from folds of membrane
11
Q
what is the function and structure of the golgi apparatus
A
role = to modify proteins and lipids before packaging them into golgi vesicles
consists of flattened sacs of membrane - looks like a WiFi symbol
- at the top is the cis face where the incoming vesicle attaches
and at the bottom is the trans face where vesicles are secreted
12
Q
centrioles
A
made of microtubules - which are filaments of protein that can be used to move substances around inside the cell
centrosome = 2 centrioles at right angles to each other. centrosome organises the spindle fibres during cell division
not found in plants and fungi
13
Q
what is the process of protein transport - involving the rER and the Golgi Apparatus
A
- the nucleolus manufactures ribosomes for protein synthesis in the rER
- the nucleus manufactures mRNA
- the ribosomes in the rER make proteins
- the rER processes the proteins which are then sent in vesicles to the golgi body
- the golgi body further processes the proteins and sends them in vesicles to the plasma membrane
6.Cells exit the Golgi in a vesicle. Extracellular enzymes are secreted by exocytosis.
14
Q
what additional structures do prokaryotes have (7)
A
- plasmids
- capsule
- flagellum
- pilus
- mesosomes
- circular DNA
- 70s ribosomes
15
Q
what is the function of pili
A
thread-like structures that help prokaryotes stick to other cells and can be used in the transfer of genetic material
16
Q
what is the function of the slime capsule
A
final outer layer that protects bacteria from drying out and from attacking cells
not present in all prokaryotes
17
Q
structure and function of mesosomes
A
inward folds in the plasma membrane.
aerobic respiration, cell wall formation and DNA replication
18
Q
what is the function of plasmids
A
small loops of DNA that contain genes that can be passed between prokaryotes
not present in all prokaryotes
19
Q
what is the function of the flagellum
A
a ling, hair-like structure that enables the prokaryote to move
not present in all
20
Q
what is the circular DNA in prokaryotes
A
the genetic material of prokaryotic cells mainly consists of a single circular strand of DNA that is not contained in a membrane-bound nucleus
21
Q
What is the difference between magnification and resolution
A
mag = increase in image size of an object
res = ability to distinguish between two separate points or objects
22
Q
What is the maximum resolution and magnification of a light microscope and an electron microscope
A
light = res - 200nm
mag = x1500- x2000
electron = res - 0.5nm
mag - 50,000,000x
23
Q
What are the principal differences between transmission electron microscopes (TEMs) and scanning electron microscopes (SEMs)?
A
TEMS = use transmitted electrons passing through a thin sample to show internal structures
SEMS = use scattered electrons from the surface to show surface details and topography
24
Q
How do you calibrate an eyepiece graticule suing a stage micrometer?
A
place the micrometer on the microscope stage, view it through the eyepiece, and align the graticule with the micrometer scale.
Then, determine the magnification factor by counting the number of graticule divisions that correspond to a known distance on the micrometer
25
what are
1. tissues
2. organs
3. organ systems
1. a group of cells of similar structure working together to perform a particular function
2. made from a group of diff tissues working together to perform a particular function
3. made from a group of organs w related functions working together to perform body functions within the organism
26
what are the phases of the cell cycle
G1
S
G2
M phase
27
what happens during phase G1
a signal is received telling the cell to divide again, the DNA in the nucleus replicates
cells make the RNA, enzymes, and other proteins required for growth
28
what happens during the S phase
synthesis of DNA
29
wha happens during the G2 phase
cell continues to grow and the new DNA that has been synthesised is checked and any errors are usually repaired
30
what stages of the cell cycle make up the interphase
G1 + S+ G2
31
what are the 4 phases of mitosis
prophase
metaphase
anaphase
telophase
32
what happens during prophase
- chromosomes condense - now visible when stained
- chromosomes consist of 2 identical chromatids = sister chromatids that are joined at the centromere
- the 2 centrosomes - replicated in G2 - move towards opposite poles
- spindle fibres begin to emerge from the centrosomes
- nuclear envelope breaks down
33
what happens during the metaphase
- centrosomes reach opposite poles
- spindle fibres continue to extend from centrosomes
- chromosomes line up @ equator of the spindle so they are equidistant to the 2 centrosome poles
- spindle fibres reach the chromosomes and attach to the centromeres
- each sister chromatid is attached to a spindle fibre from opposite poles
34
what happens during anaphase
- the sister chromatids separate at the centromere
- spindle fibres begin to shorten
- sister chromatids, now called chromosomes, are pulled to opposite poles by the spindle fibres
35
what happens during telophase
-chromosomes arrive @ opposite poles and begin to decondense
- nuclear envelopes begin to reform around each set of chromosomes
- the spindle fibres break down
36
what happens during cytokinesis
whole cell divides, creates 2 genetically identical daughter cells
37
what is mitosis used for
growth
repair
asexual reproduction
38
how do u calculate mitotic index
number of cells w visible chromosomes / total number of cells
39
how is an egg specialised to its function
- much larger bcoz most of their internal space contains nutrients for a growing embryo
- have zona pellucida (jelly-like glycoprotein layer) that forms an impenetrable barrier after fertilisation
40
how are sperm cells adapted for their function
- flagellum - enables to swim to egg
- enzymes in acrosome - to digest through zona pellucida
- many mitochondria - provide energy to swim
41
describe the process of fertilisation
- sperm cell membrane fuses with egg cell membrane
- acrosome releases enzymes that digest through ZP
- cortical granules release contents into zona pellucida
- contents of cortical granules react with the zona pellucida and the ZP thickens
- the haploid nuclei fuse
42
what is the cortical reaction
when the chemicals contained within the cortical granules cause the zona pellucida to rapidly thicken preventing any more sperm cells from entering
43
what is the acrosome reaction
when the acrosome releases enzymes that digest a path through the zona pellucida allowing the sperm to pass through the egg cell membrane
44
describe the process of meiosis
- chromosomes replicate before meiosis
- during meiosis, the homologous pairs of chromosomes split up to produce 2 haploid nuclei
- then the chromatids that make up each chromosome separate to produce 4 haploid nuclei
- each chromosome now consists of a single chromatid
45
what are the two factors that create genetic variation
mutations
sexual reproduction
46
What is crossing over of chromatids?
process where non-sister chromatids exchange alleles
1. homologous chromosomes pair up - called bivalents
2. the non-sister chromatids can cross over and get entangled
3. these crossing points are called chiasmata
4. the entanglement places stress on the DNA molecules, as a result of this, a section of chromatid from one chromosome may break and rejoin w the chromatid from the other chromosome
47
why is the swapping of alleles significant
+ where is crossing over more likely to occur?
it can result in a new combination of alleles on the two chromosomes
crossing over is more likely to occur further away from the centromere
48
what is the independent assortment of chromosomes
random alignment of homologous chromosome pairs during meiosis, leading to diff allele combinations in daughter cells
1. homologous chromosomes pair up and move to the spindle equator
2. each pair aligns randomly, with either chromosome on top
3. the orientation of one pair is independent of others
4. homologous chromosomes are then separated and pulled to opposite poles
49
what is a totipotent cell?
can differentiate into any cell type
zygote and cells up to 16-cell stage are totipotent
50
what is a pluripotent cell
can differentiate into any embryonic cell type
cannot form placenta or umbilical cord
found in embryonic stem cells
51
what are stem cells
an undifferentiated cell that can divide by mitosis an unlimited number of times
52
what is potency
the ability of stem cells to differentiate into more specialised cell types
53
where do plants have stem cells
shoots and roots
54
what are some examples of adult multipotent stem cells
bone marrow
skin
liver
brain
umbilical cord blood
55
how are EMBRYONIC stem cells used in medicine?
totipotent if taken 3-4 days after fertilisation
pluripotent if taken on day 5
embryos used are often waste fertilised embryos from IVF
56
issues with ADULT stem cells being used in medicine
- only able to differentiate into a limited range of cell types
- need to be a close match for blood type and antigens
57
what is a gene?
a section of DNA that codes for a single polypeptide or protein
58
what is a locus (loci)
the position of a gene on a chromosone
59
how have scientists found the specific physical loci of genes
through experiments and genetic mapping
60
what is an autosome? what happens during autosomal linkage
autosome = any chromosome that isn't a sex chromosome
- two or more genes on the same autosome do not assort independently during meiosis, these genes are linked and stay together in the original parental combination
61
what happens during sex linkage when the gene is on the X chromosone
men will only have one copy of the gene, females will have 2
- males are more likely to show sex-linked recessive conditions
- females, are likely to inherit one dominant allele that masks the effect of the recessive allele
62
how are proteins made and modified? (Golgi Apparatus and ER)
transcription of DNA and mRNA in nucleus, then mRNA leaves nucleus.
Protein is translated on the ribosomes of the rER and moves thru the ER - gaining its 3D shape. Then moved in a vesicle to fuse w the sacs of the Golgi.
Here the proteins are modified, before being pinched off into vesicles and fused with the cell membrane to be released
63
what is the role of differential gene expression in stem cell differentiation?
differential gene expression means only certain genes in a stem cell are activated and expressed, leading to specialisation.
64
do stem cells in a multicellular organism have the same DNA
yes, they all contain the same DNA, but express different genes depending on their function
65
how do genetically identical stem cells become different specialised cells?
by expressing different sets of genes.
66
what triggers differentiation in stem cells?
specific conditions activate some genes, and inactivate others
67
what are the steps of differentiation?
- mRNA is transcribed from active genes only
- mRNA is then translated to form proteins that are responsible for modifying the cell's structure and function
- as the proteins continue to modify the cell, the cell becomes increasingly specialised
- specialisation process is irreversible
68
what is a transcription factor and what is its role in gene expression?
a transcription factor is a protein that binds to specific regions on DNA to control gene transcription, ensuring genes are expressed in the right cells, at the right time, and to the correct level
69
what is the function of transcription factors in organisms
allow cells to respond to internal and external signals by regulating gene expression, which is key to development and environmental adaptation
70
how do activator and repressor transcription factors differ
- activators increase transcription by helping RNA polymerase bind to DNA.
- Repressors decrease transcription by preventing RNA polymerase from binding
71
where do some transcription factors bind... and what effect does this have?
often bind to the promoter region of a gene, either facilitating or inhibiting the binding of RNA polymerase.
72
what is an operon and what are its key components
an operon is a DNA section in prokaryotes that includes structural genes, promoter region, operator region, and sometimes a regulatory gene coding for repressors or activators
73
what is the function of the lac operon in bacteria
a structural gene that controls production of enzymes like lactase - which breaks down lactose so it can be used as an energy source.
only metabolises lactose when lactose is present .: it is inducible
74
what is the order of components in the lac operon and their functions?
1. promoter (RNA polymerase binds)
2. operator (repressor binds)
3. lacZ - codes for lactase
4. lacY - codes for permease
5. lacA - codes for transacetylase
74
how does the lac repressor protein regulate gene expression in the lac operon?
the lac repressor, coded by lacI, binds to the repressor, changing its shape so it cant bind the operator - allowing RNA polymerase to transcribe the structural genes
75
what happens in the absence of lactose in the lac operon system
the lacI gene is expressed, producing the lac repressor protein, which binds to the operator, blocking RNA polymerase from binding to the promotor, so no transcription or lactase production occurs
75
what happens in the presence of lactose in the lac operon system?
lactose enters the cell and binds to the lac repressor, changing its shape so it cant bind to the operator. This allows RNA polymerase to bind to the promotor and transcribe the structural genes
76
what is the result of transcription in the lac operon when lactose is present?
mRNA from lacZ, lacY, and lacA is translated, producing lactase, permease and transacetylase, enabling the bacterium to metabolise lactose as an energy source.
77
what are cells, tissues and organs?
cells = smallest structural and functional unit of all living organisms
tissues = group of cells with a similar structure and function
organs = group of tissues that perform specific functions
78
how can environmental factors influence gene expression?
environmental stimuli can alter levels of transcription factors or regulatory proteins, changing gene expression patterns
79
what is epigenetics
epigenetics = control of gene expression by factors other than DNA sequence, involving the switching on and off of genes without changing the genetic code
80
what are the 2 main types of epigenetic modifications and how do they affect gene expression
DNA methylation - addition of CH3 groups
2. Histone acetylation - modifies histone tails
- these alter how tightly DNA is wound around histones, affecting accessibility to RNA polymerase and transcription factors
81
what is the epigenome and how is it affected
epigenome is the full set of epigenetic tags in an organism.
it is influenced by environmental factors - stress, diet, smoking etc - and internal signals, and can vary with age.
histone modification is reversible
82
what is DNA methylation and how does it affect gene expression?
DNA methylation is the addition of methyl groups to cytosine bases, repressing gene expression by preventing transcription factor and RNA polymerase binding - locking genes in the 'off' position
83
what factors can influence DNA methylation
environmental, lifestyle and age related factors
84
how does histone acetylation affect gene expression
acetylation of lysine residues on histones, neutralises their positive charge, loosening DNA-histone interaction and allowing easier access for RNA polymerase - activating gene expression
85
what is the effect of histone deacetylation on gene expression
deacetylation restores the positive charge on lysines, tightening DNA around histones and preventing access by transcription machinery - repressing gene expression
86
can epigenetic changes be inherited during cell division
yes - it is heritable, maintaining patterns of gene expression
87
how can epigenetic changes be passed onto offspring
during gamete formation, DNA usually undergoes demethylation, but some methyl groups may remain. if the changes are adaptive, they may be passed onto offspring, potentially preparing them for similar environmental conditions
88
what is a phenotype. and what causes phenotype variation?
a phenotype is an organisms observable characteristics. variation can be caused by genetic differences, environmental influences, or both
89
give examples of phenotypic variation caused by genetics, environment, and both
genetic: human blood groups (ABO gene)
environmental: cloned plants growing to different heights
both: sickle cell anaemia - genotype provides malaria resistance in certain environments
89
what is genetic variation and how is it inherited?
small difference in DNA base sequences between individuals of the same species, it is inherited and causes phenotypic variation within a population
90
What is the difference between monogenic and polygenic traits?
Monogenic: Controlled by one gene, shows discontinuous variation (e.g. blood group)
Polygenic: Controlled by multiple genes, shows continuous variation (e.g. height)
91
How can environmental factors affect phenotype without altering genotype?
Environmental conditions like light, water, nutrients, temperature, etc., can affect gene expression and growth, e.g. chlorosis or etiolation in plants, or diet-induced colour change in fruit flies.
92
Why can’t phenotypic changes caused solely by the environment be inherited?
Because they don’t alter the DNA in gametes, only genetic changes can be passed to offspring.
93
What is discontinuous variation, and what causes it?
Discontinuous variation is caused by qualitative differences in phenotype. Traits fall into distinct categories with no intermediates (e.g. blood groups). It's often controlled by a single gene (monogenic).
