Lecture 2 Genetics Flashcards
Lecture 2 Genetics
1
Q
In Eukaryotes, how does the transmission of genetic material occur?
A
Via chromosomes involving Mitosis and Meiosis
2
Q
Meiosis leads to the production of _____. Mitosis leads to the production of ____
A
- Meiosis: Sex cells/Germ-line cells/ Gametes or Spores
- Mitosis: Two cells with the same number of chromosomes as parent cell (2n)
3
Q
Define Chromatin
A
During non-divisional phases, chromosomes uncoil into a diffuse network within the nucleus
4
Q
There are two main types of cells: Prokaryotic (bacteria and archaea) + Eukaryotic (protists, plants, fungi, and animals)
All cells share some common features such as:
A
- Plasma membrane
- DNA
- Ribosomes
5
Q
Compare Karyokinesis and Cytokinesis. Also, which division is INDEPENDENT?
A
- Karyokinesis: Splitting in the nucleus
- Cytokinesis: Splitting of cytoplasm
- Mitochondrial division is independent
6
Q
Define Plasma Membrane. Also, compare plants and bacterial plasma membranes.
A
- Surrounds all cells
- Delimits cells from the external environment
- Plants: Have plasma membrane and cell wall composed mainly of cellulose (polysaccharide)
- Bacteria: Peptidoglycan in their cell walls
7
Q
Define Glycocalyx or Cell Coat
A
- “Sugar Coat”
- Covering on plasma membrane of animal cells
- Made of glycoproteins and polysaccharides
- Function: Biochemical identity at cell surface
8
Q
What are Receptor Molecules?
A
- Found on the surface of cells
- Recognition sites that transfer specific chemical signals across the cell membrane into the cell
9
Q
Explain the Nucleus
A
- Found in eukaryotes
- Membrane bound’
- Houses genetic material (DNA)
10
Q
Explain the Nucleolus. Also, explain the Nucleolus Organizer Region
A
- Where ribosomal RNA (rRNA) is synthesized
- Nucleolus Organizer Region (NOR): DNA that encodes rRNA
11
Q
Explain the Nucleoid
A
- Found in prokaryotes
- Not membrane bound
12
Q
What organelles have 2 membranes?
A
- Nucleus
- E.R.
- Chloroplast
- Mitochondria
13
Q
Cytoplasm includes what contents?
A
- Extra nuclear cellular organelles
- Cytosol
- Cytoskeleton
14
Q
Define Cytosol
A
Cytosol: Soluble/liquid portion in the cytoplasm, also known as colloidal materials surrounding organelles
15
Q
Define Cytoskeleton + its content
A
Cytoskeleton: Made of extensive system of tubules and filaments
- Microtubules: Made up of the protein tubulin
- Microfilaments: Derived from the protein actin
16
Q
What do microtubules and microfilaments allow?
A
Allow movement of other molecules in the cytoplasm = Cytoplasmic Streaming
17
Q
What is the function of the Endoplasmic Reticulum?
A
- Compartmentalizes cytoplasm
- Increases surface area for biochemical synthesis
18
Q
What is the function of Smooth Endoplasmic Reticulum?
A
Site of fatty acid and phospholipid synthesis
19
Q
What is the function of Rough Endoplasmic Reticulum?
A
- Site of protein synthesis
- “Rough” = Studded with ribosomes
20
Q
What is the function of Mitochondria?
A
Site of oxidative phases of cell respiration, which generated ATP
21
Q
What is the function of Chloroplast? Which organisms possess it?
A
- Site of photosynthesis
- Fixation of atmospheric CO2
- Found in Plants, Algae, and Protozoans
22
Q
What is the function of centrioles? Where are they found + what are they made of?
A
- Function: Organize spindle fibers for movement of chromosomes during meiosis and mitosis
- Found in animal and plant cells
- Made of microtubules
23
Q
In diploid organisms, chromosomes exist in _____ ______
A
Homologous Pairs
24
Q
Define Homologous Chromosomes
A
- Similar, but NOT identical
- Carry genes for the same inherited characteristics
- May carry different versions of the same gene called alleles
25
Sister chromatids with centromere have two types of arms. Describe them
- Long arm = q arm
- Short arm = p arm "petite"
26
Explain Centromeres and the 4 different locations
- Constricted regions on chromosomes
- Location of centromere establishes appearance of chromosome
- Locations include: Metacentric, Submetacentric, Acrocentric, and Telocentric
27
What is a fun way to describe Kinetochores?
"Like screws" to which fibers attach which helps with how chromosomes will be pulled
28
Explain the # of chromosomes in Body cells. Also, what are some exceptions?
- Body cells also known as Somatic cells have homologous pairs of chromosomes
- Humans: 46 chromosomes (23 homologous pairs)
- Represents diploid number, 2n
- Exceptions: Many bacteria and viruses with one chromosome AKA Haploid
29
Define Karyotype
- Illustrates the physical appearance of the different pairs of homologous chromosomes
- The human mitotic chromosomes have been photographed, cut out of the print, and matched up.
30
Define Genome
- Total genetic information
- Genetic information in haploid set
31
_____ converts the diploid number (2n) of chromosomes to the haploid number (n)
Meiosis
32
Define Locus (Loci)
- Each site on homologous chromosomes containing identical gene sites along their lengths
33
What is Biparental Inheritance?
- Inheritance from two parents
- NOTE: Diploid organisms contain two copies of each gene
34
Define Alleles
Alternative forms of the same genes can exist
35
Explain Sex-determining chromosomes. Provide an example
- NOT homologous
- Behave as homologs in meiosis w/ Meiotic Recombination
- Ex.) X and Y chromosomes in humans
36
Define Zygote
Single-celled fertilized eggs of multicellular organisms
37
Define Karyokinesis
Genetic material partitioned to daughter cells during nuclear division
38
Define Cytokinesis
Cytoplasmic division
39
Describe the Cell Cycle
- Composed of interphase and mitosis
- Interphase includes the S phase (DNA synthesized here) and 2 gap phases (G1 and G2)
- G0: Point in G1 phase where cells are nondividing but in a metabolically active state "Quiescent aka quiet phase"
- NO DNA duplication in GAP phases
40
Define Interphase
Characterized by the absence of visible chromosomes
41
Define Prophase
- Centrioles divide, move, and establish poles
- Nuclear envelope breaks down
- Chromosomes condense and become visible
42
Define Prometaphase
- Period of chromosome movement to equatorial plane of cell
- Equatorial plane referred to as metaphase plate
- Centrioles reach poles
- Spindle fibers form
43
Define Metaphase
- Chromosome configuration following migration
- Centromeres align on metaphase plate
- Kinetochore microtubules have one end near the centrosome region and the other end anchored to the kinetochore
- Cohesin, Separase, and Shugoshin are also involved here. (defined in other flashcards)
44
Define Kinetochore
- Proteins associated with centromere
- Spindle fibers bind to kinetochore; chromosome migrate
45
Define Cohesin during Metaphase
Protein complex that holds sister chromatids together
46
Define Separase during Metaphase
Enzyme that degrades cohesin
47
Define Shugoshin during Metaphase
Protein that protects cohesin from being degraded by separase
48
Define Anaphase
- Disjunction
- Sister chromatids separate now called sister chromatids
- Migrate to opposite poles by shortening of spindle fibers
- Motor proteins or molecular motors use ATP
49
Define Telophase
- Uncoiling of the chromosomes
- Reformation of the nuclear envelope
- Spindle fibers disappear
- Nuclear envelope reforms
50
Define Cytokinesis
- Two new cells are produced
- Note: Plant cells have a cell plate that is synthesized and laid down across the metaphase plate which becomes the middle lamella
- Note: Animal cells have a constriction of the cytoplasm or cell furrow
- DO NOT FORGET that organelles such as the mitochondria also separate to form these daughter cells
51
Explain Cell Division Cycle (CDC) Mutations
- Enzymes called kinases
- Can add phosphates to other proteins to regulate the cell cycle
- Are "Master Control" molecules functioning in conjunction with cyclin proteins
- Cyclin = Gatekeeper for PMAT
52
What do the Cell cycle checkpoints do?
- Monitor mitosis for errors
53
During which phase of MITOSIS does a cell last the longest? Why?
Prophase (36 min) due to chromatin condensation with Histones
54
Explain what happens during each of the Checkpoints
- G1/S checkpoint: Undamaged DNA and correct size/resources for synthesis to occur
- G2/M checkpoint: Prevents mitosis until correct DNA for it to occur
- M checkpoint: Proper formation of spindles and kinetochore attachment
55
What occurs during Meiosis?
- Reduces amount of genetic material by half
- Produces haploid gametes or spores, each containing one member of a homologous pair of chromosomes
56
What produces the Variability in Meiosis?
Crossing Over in Prophase 1 of Meiosis where genetic exchange between members of homologous pairs of chromosomes
57
Classify Meiosis 1 and 2 by their divisions
- Meiosis1: Reductional division
- Meiosis 2: Equational division
58
When does DNA synthesis occur/not occur during Meiosis?
- Occurs during Interphase, before the beginning of Meiosis 1
- Does NOT occur again before Meiosis 2
59
When can Nondisjunction occur in Meiosis?
Can occur in Meiosis 1 or 2 because it usually occurs during the Anaphase stage. In Meiosis 1 it may occur to the Homologous chromosomes or in Meiosis 2 with the sister chromatids
60
Define Chiasma
Where recombination takes place between two non-sister chromatids of homologous chromosomes where genetic material is exchanged during the process of crossing over
61
What are the substages of Prophase 1? Define them!
1. Leptonema: Chromosomes appear as long, single threads, unassociated with each other
2. Zygonema: "Rough Pairing", Synapsis, Each pair of homologous chromosomes is known as bivalent
3. Pachynema: Each bivalent becomes shorter, thicker, and splits into two sister chromatids called tetrads. CROSSING OVER OCCURS HERE!
4. Diplonema: Within tetrads, sister chromatids separate. Chiasma found here which is where chromatids are still intertwined
5. Diakinesis: Nucleus and nuclear envelope break down. Centromeres attach to spindle fibers
62
Define Metaphase 1
- Chromosomes at maximum shortness
- Terminal chiasmata holding sister chromatids together
- Binding to spindle fibers moves chromatids to metaphase plate
63
Define Anaphase 1
- Cohesin is degraded between sister chromatids
- Homologous chromosomes separate
- Nondisjunction MAY occur
64
Define Telophase 1
- Two haploid cells result
- Nuclear membranes forms
- Nuclei enter interphase
65
Summary of Metaphase 1, Anaphase 1, and Telophase 1
- Homologous chromosomes separate and move toward the poles
- Sister chromatids remain attached at centromeres
- Duplicated chromosomes reach poles. Each pole now has haploid set of chromosomes
- Cytokinesis: Two haploid daughter cells are formed
- Nuclear envelope forms around chromosomes in some species
- NOTE: Meiosis significantly increases the level of genetic variation due to crossing over
66
Explain Meiosis 2
- Prophase 2: Each dyad is composed of one pair of sister chromatids attached by the common centromeric region
- Metaphase 2: The centromeres are positioned on the equatorial plate
- Anaphase 2: Sister chromatids are separated at the opposite poles
- Each haploid daughter cell from meiosis 2 has one member of each pair of homologous chromosomes
- Telophase 2: One member of each pair of homologous chromosomes present at each pole which is where each chromosome is now a MONAD
- Cytokinesis results in 4 haploid cells
67
Explain Spermatogenesis
- Primary spermatocyte undergoes meiosis 1, producing 2 secondary spermatocytes
- Spermatocytes undergo meiosis 2, producing a total of 4 haploid spermatids
68
_____ is CRITICAL to the successful sexual reproduction of ALL diploid organisms
Meiosis!!!!
- Mechanism by which diploid amount of genetic information is reduced to haploid
68
Explain Oogenesis
- Formation of Ova in the Ovaries
- 4 daughter cells do NOT receive equal cytoplasm
- Only 1 daughter cell receives cytoplasm (Primary Polar Body), which undergoes meiosis 1 and 2. This can develop into ovum
69
Briefly describe the Plant and Fungi Life Cycles
- Fungi: Haploid vegetative cells arise via meiosis - proliferative via mitotic cell division
- Plants: Life cycle alternates between diploid sporophyte stage and haploid gametophyte stage
