Week 1 Flashcards
Mitosis and meiosis (78 cards)
1
Q
What is cell division?
A
The process by which cells make more cells
2
Q
What are the four main reasons cells divide?
A
- Growth
- Cell replacement
- Healing
- Reproduction
3
Q
What type of cells undergo mitosis?
A
Stem cells
4
Q
What type of cells undergo meiosis?
A
Sex cells
5
Q
Describe the genome of eukaryotic cells
A
Large and linear
6
Q
Where is DNA located in eukaryotes?
A
The nucleus
7
Q
Describe the genome of prokaryotic cells
A
Small and circular
8
Q
Where is DNA located in prokaryotes?
A
The cytoplasm
9
Q
What are the two stages of the cell cycle?
A
- M phase (mitosis or meiosis)
- Interphase
10
Q
What are the four stages of interphase (in order)?
A
- G1 phase
- S Phase
- G2 phase
- G0 phase (mitosis only)
11
Q
What occurs during the G1 phase of interphase?
A
Growth, cellular metabolism
12
Q
What occurs during the S phase of interphase?
A
DNA replication (chromosome duplication)
13
Q
What occurs during the G2 phase of interphase?
A
Preparation for mitosis/meiosis
14
Q
What occurs during the M phase of the cell cycle?
A
Chromosomal separation and cytokinesis
15
Q
What is interphase?
A
The time between successive cell division (G1, S, G2)
16
Q
What is the state of a cell when it exits the cell cycle?
A
G0
17
Q
In what state are cells said to be quiescent?
A
G0
18
Q
How many chromosomes are in the human genome?
A
46 chromosomes (23 pairs)
19
Q
What are homologous chromosomes?
A
Pairs of chromosomes of the same type (carrying the same set of genes)
20
Q
What are centromeres?
A
The constriction site that holds sister chromatids together
21
Q
What are sister chromatids?
A
Two identical copies of a chromosome produced by DNA replication
22
Q
What does ploidy describe?
A
The number of complete sets of chromosomes in a cell
23
Q
What is a haploid cell?
A
A cell with one complete set of chromosomes
24
Q
How are haploid cells denoted?
A
n
25
What is an example of a haploid cell?
A human sperm or egg cell
26
What is a diploid cell?
A cell with two complete sets of chromosomes (one from father, one from mother)
27
How are diploid cells denoted?
2n
28
What is an example of a diploid cell?
Somatic cells
29
Why are cells still considered diploid after S phase (even though there are now 4 complete sets of chromosomes)?
- The amount of DNA/chromosomes changes, but the actual type doesn't
- It is a short and transient phase
30
In mitosis, the amount of _____ changes, but not the ________ ________.
DNA, ploidy level
31
What is a polyploid cell?
A cell with four or more complete sets of chromosomes
32
What are the five stages of mitosis (in order)?
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
33
What occurs during prophase of mitosis?
- Chromosomes condense
- Centrosomes radiate microtubules (aka mitotic spindles) and migrate to opposite poles
34
What occurs during prometaphase of mitosis?
- The nuclear envelope breaks down
- Microtubules of the mitotic spindle attach to the centromeres of chromosomes
35
What are kinetochores?
The protein complex where spindle fibres attach on each side of the centromere
36
What occurs during metaphase of mitosis?
Chromosomes align in the centre of the cell
37
What occurs during anaphase of mitosis?
Sister chromatids separate into individual chromosomes (when the centromere splits) and travel to opposite poles
38
What occurs during telophase of mitosis?
The nuclear envelope re-forms and chromosomes decondense
39
What is cytokinesis?
Occurs at the end of mitosis to create two seprate daughter cells
40
What is the difference between cytokinesis in plant cells and animal cells?
- Animal cells form a contractile ring and pinch apart
- Plant cells don't pinch apart, they form a cell plate (new cell wall) and split
41
What is the result of a cell undergoing mitosis but not cytokinesis?
A multinucleate cell
42
T or F: Mitosis can continue in perpetuity
True
43
What is meant by saying meiosis is a terminal event?
It's the last "step" of cell division
44
What is the result of the first division in meiosis (meiosis I)?
Homologous chromosomes are randomly separated
45
What is the result of the second division in meiosis (meiosis II)?
Sister chromatids are split
46
How does the end result of mitosis differ from meiosis?
- Mitosis: 2 identical daughter cells
- Meiosis: 4 unique daughter cells
47
What is the ploidy level of the products of mitosis?
Daughter cells are diploid (2n)
48
What is the ploidy level of the products of meiosis?
Daughter cells are haploid (n)
49
What are the stages of meiotic cell division?
- Interphase
- Meiosis I
- Meiosis II
- Meiotic division of cytoplasm
50
What are the stages of meiosis I?
- Prophase I
- Prometaphase I
- Metaphase I
- Anaphase I
- Telophase I and cytokinesis
51
What are the stages of meiosis II?
- Prophase II
- Prometaphase II
- Metaphase II
- Anaphase II
- Telophase II and cytokinesis
52
When does crossing over occur?
Prophase I of meiosis
53
What is crossing over?
When non-sister chromatids physically break and exchange maternal and paternal genetic material
54
In terms of cell division, what is synapsis?
The gene for gene pairing of homologous chromosomes
55
What are non-sister chromatids?
The chromatids (with different centromeres) that are attached in the bivalent
56
T or F: Non-sister chromatids are identical.
False. They carry the same set of genes in the same order, but are not genetically identical (one is maternal and one is paternal).
57
What is a bivalent?
The four stranded chromosomal structure composed of a pair of synapsed chromosomes (two pairs of sister chromatids aligned along their length)
58
What is the chiasma?
The visible manifestation of a crossover within bivalents
59
What are recombinant chromatids?
The result of crossing over at chiasmata between non-sister chromatids
60
What holds the bivalents together during while they become oriented during metaphase I?
Chiasmata
61
T or F: The positions of crossovers along the chromosome are random.
True
62
What are the main 5 things that occur during prophase I of meiosis?
- Chromosomes become visible (replication is already complete)
- Homologous chromosomes undergo synapsis
- Bivalents are formed by each pair of homologous chromosomes (when synapsis is complete)
- The chiasmata between non-sister chromatids become apparent (the result of crossing over)
- The nuclear envelope begins to break down
63
What occurs during prometaphase I of meiosis?
Spindles attach to kinetochores on chromosomes
64
What occurs during metaphase I of meiosis?
Homologous chromosomes line up in the centre of the cell
65
How are bivalents oriented during metaphase I of meiosis?
Bivalents are oriented randomly with respect to each other
66
How does kinetochore attachment differ between mitosis and meiosis I?
- Mitosis: Sister kinetochores are attached to opposite sides of the chromosome
- Meiosis I: The kinetochores orient side by side on one side of the chromosome (mono orientation)
67
What occurs during anaphase I of meiosis?
Homologous chromosomes separate, but sister chromatids do not
68
What occurs during telophase I and cytokinesis of meiosis?
- A nuclear envelope briefly reappears
- Cytoplasm divides and two separate cells are formed
69
What is the ploidy level of cells after cytokinesis of meiosis I?
The two daughter cells are haploid (n) because both the amount and type of DNA have been reduced
70
What occurs during prophase II of meiosis?
The nuclear envelope breaks down and the chromosomes condense
71
What occurs during prometaphase II of meiosis?
Spindles attach to kinetochores on chromosomes
72
What occurs during metaphase II of meiosis?
Chromosomes align in the centre of the cell
73
What occurs during anaphase II of meiosis?
Sister chromatids separate
74
What occurs during telophase II and cytokinesis of meiosis?
The nuclear envelope re-forms and the cytoplasm divides
75
T or F: In multicellular organisms, division of cytoplasm during meiotic cell division differs between sexes
True.
76
How does cytoplasm divide among female cells undergoing meiosis?
- Meiosis I: Cytoplasm divides unequally, resulting in one oocyte and one polar body
- Meiosis II: Cytoplasm of oocyte divides unequally, resulting in one functional ovum (after maturation) and another polar body (polar body from meiosis I also divides and creates two polar bodies)
77
What are the final products of meiotic division of cytoplasm in female mammals?
One oocyte and three polar bodies
78
How does cytoplasm divide among male cells undergoing meiosis?
Cytoplasm divides equally in both meiotic divisions, resulting in four unique sperm cells
