Cell Division: Mitosis & Meiosis Flashcards
1
Q
What is Karyokinesis?
A
partition of the nucleus/formation of 2 new nuclear membranes
2
Q
What is Cytokinesis?
A
division of the cytoplasm and cell membrane/formation of 2 new cell membranes
3
Q
What are the two phases of the cell cycle?
A
Interphase and Mitosis
4
Q
What are the different phases within interphase?
A
G1, S, G2
5
Q
What are the phases within mitosis?
A
prophase, metaphase, anaphase, telophase
6
Q
How long is a cell in the interphase and mitosis stages?
A
Interphase- 90% ~20hr
Mitosis- 10% ~2hr
7
Q
What is involved in the G1 phase?
A
cell growth, transcription, translation, and G0
8
Q
What is involved in the S phase?
A
(synthesis); DNA replication
9
Q
What is involved in the G2 phase?
A
Check for any DNA damage and repair
10
Q
What is involved in Mitosis?
A
separation of sister chromatids, karyokinesis, and cytokinesis
11
Q
In the cell cycle, when is a nuclear membrane present?
A
G1 to prophase
12
Q
In the cell cycle, when are there no visible chromosomes?
A
G1 through G2
13
Q
What is a checkpoint in the cell cycle?
A
transition from step to step
14
Q
What are checkpoints regulated by?
A
> 1000 genes/proteins and many microRNAs
15
Q
What are cycllins?
A
groups of proteins; level of the proteins changes throughout the cycle
16
Q
What are cyclin dependent kinases?
A
they attach phosphates to other proteins and activate them
17
Q
What are phophatases?
A
they remove protein groups
18
Q
What so transcription factors do?
A
specific ability to bind directly to DNA and trigger transcription of certain genes
19
Q
What are the chromatin modifying proteins? (5)
A
TOPOisomerase II
Cohesin
Separase
Securin
Microtubules Associated Proteins (MAPs)
20
Q
What is the function of TOPOisomerase II?
A
unwinds DNA double helix
21
Q
What is the function of cohesin?
A
keeps sister chromatids together
22
Q
What is the function of separase?
A
cleaves cohesin and separates centromeres
23
Q
What is the function of securin?
A
triggers anaphase, transports separase to the nucleus
24
Q
What are some examples of MAPs?
A
kinesins, dyneins
25
In the S phase, how many different "phases" are there and what are they?
2: early replication and late replication
26
What is present during the early replication "phase" of the S phase?
transcriptionally active DNA
27
What is present during the late replication "phase of the S phase?
inactive DNA; heterochromatin
28
What is the result of mitosis?
equal division of genetic material and the formation of two new daughter cells
29
What occurs during prophase?
chromosomes begin to condense, sister chromatids become visible, nucleolus disintegrates, nuclear membrane breakdown
30
What is a centrosome?
microtubule organizing center. Composed of centrioli which divide and move apart
31
What occurs during prometaphase?
chromsomes move towards midline and condensing continues, sister chromatids become visible, formation of spindles, no nuclear membrane, and chromosomes attach to spindles
32
What does DNA decatenation mean?
the sister chromatids become visible
33
What occurs during metaphase?
maximum chromosome condensation, chromosomes attach to spindles at both poles, kinetochores under tension
34
What does colchicine do?
"spindle poison" causes damage to the spindles and arrests mitosis
35
What occurs during anaphase?
split of the centromeres, separation of the sister chromatids, sister chromatids pulled apart and moved to separate poles
36
After disjunction, what are sister chromatids called?
daughter chromosomes
37
What occurs during telophase?
daughter chromosomes arrive at the poles, karyokinesis, decondensation pf chromosomes, cytokinesis
38
How many checkpoints are there in the cell cycle?
4
39
What is the G1-S checkpoint for?
whether or not the cell qualifies for cell division
40
What is the S-G2 checkpoint for?
TO check that all the DNA is replicated and that it has only been replicated once
41
What is the G2-M checkpoint for?
To check if the DNA is damaged and repair it
42
What is the M checkpoint for?
To check that spindle is well attached to the kinetochore
43
What is the biological function of Mitosis?
- replicate genetic material and divide it equally/without mistakes between daughter cells
- growth, replacement, and maintenance of cells
44
What are the essentials of mistosis?
- homologous chromosomes behave independently from each other
- disjunction/separation of sister chromatids
- chromosome # before=chromosome # after
45
Which type of cells undergo diploid mitosis and what is the purpose?
Somatic cells; for growth and development
46
What type of cell undergo haploid meiosis and what is the purpose?
Germ cells; for sexual reproduction
47
What happens to the genetic material in cells that under go mitosis?
Remains the same
48
What happens to the genetic material in cells that undergo meiosis?
It is cut in half
49
How many stages are in Meiosis Prophase I and what are they?
There are 5
1. leptonema
2. zygonema
3. pachynema
4. diplonema
5. diakinesis
50
What happens in the leptonema stage of prophase I?
stage 1: chromatin condenses and is the start of homology search
51
What are chromomeres?
bread like irregularly spaced condensations
52
What happens in the zygonema stage of prophase I?
stage 2: continuation of condensation, homologs find each other, formation of bivalents, start of synapsis
53
What are bivalents?
two homologous chromosomes
54
What does synapsis mean?
homologous pairing
55
What happens in the pachynema stage of prophase I?
stage 3: pairing and synapsis complete, formation of tetrads, starting of crossing over
56
What are tetrads?
A group of sister chromatids (2) and non-sister chromatids (2)
57
What is crossing over?
the genetic exchange between two non-sister chromatids
58
What happens in the diplonema stage of prophase I?
stage 4: crossing over is complete, non-sister chromatids start to separate
59
What is the biological importance of crossing over?
generates new combinations of parental genetic material
source of genetic variability
corrects mutations
60
What is a chiasmata?
reflects the site of recombination (cross overs)
61
What happens in the diakinesis stage of prophase I?
stage 5: tetrad appearance fades, chiasma becomes less visible/moves toward end of tetrad, nucleolus and nuclear envelope dissolve
62
How many cell divisions happen after prophase I and what are they?
two:
1. metaphase I --> telophase I
2. metaphase II --> telophase II
63
What happens during metaphase I?
each tetrad has 2 centromeres, terminal chiasmata hold non-sister chromatids together, orientation on metaphase plate random
64
What happens during anaphase I?
separation of homologous chromosomes (dyads are mixture of parental genomes)
65
What happens during telophase I?
cytokinesis and karyokinesis
66
Is there an interphase phase in meiosis? If so, how is it different than that in mitosis?
Yes, there is NO DNA replication. Only for transcription and translation
67
What happens during metaphase II --> telophase II?
Similar process to mitosis, results in 4 haploid gametes, each monad is a mixture of parental genomes
68
To ensure proper segregation of homologs how many crossovers must occur during the first meiotic division?
At least one per meiotic chromosome pairs
69
What does DSBs stand for?
meiotic DNA double-strand breaks
70
Formation of crossovers is strictly dependent on what?
formation and subsequent repair of DSBs
71
How are DSBs repaired?
homologous recombination
72
What are DSBs produced by?
topoisomerase related protein SPO-11
73
On average, how many meiotic DSBs are produced on a single chromosome pair?
2 (bivalent)
74
Repairs of DSBs result in either...
cross overs (Holliday junction intermediate) or non-cross overs
75
What protein binds to recombination hotspots?
PRMD9 (zing finger protein)
76
How does frequency of recombination differ between males and females?
females have a higher rate of recombination than males
77
What causes a higher rate of recombination?
more short chromosomes, at distal end of chromosomes, GC rich DNA and genes
78
The frequency of recombination is regulated by what?
chromatin structure (open/close) and chromatin marks (histone methylation)
79
What are hotspots?
short regions distributed all over the genome where recombination can occur
80
Where is the highest recombination rate known to be?
Major Histocompatibility Complex (MHC)
The Pseudo Autosomal Region (PAR)
81
What are cold spots?
Place where recombination does not occur
82
What is the best known cold spot?
centromeres
83
List the steps of spermatogenesis (in order) and whether the step is diploid or haploid.
spermatogonium (2n)
primary spermatocyte (2n)
secondary spermatocyte (n)
spermatids (n)
spermatozoa (n)
84
List the steps of oogenesis (in order) and whether the step is diploid or haploid.
primordial germ cells
oogonium (2n)
primary oocyte (2n)
secondary oocyte/first polar body (n)
ootid/secondary polar body (n)
ovum (n)
85
Why is there an unequal division of cytoplasm between an oocyte and the first polar body?
Necessary for embryonic development
86
What happens to the number of oocytes as a female matures?
They decrease
87
When does meiosis II take place in females?
Only after fertilization
88
What is dictyate?
When oogenesis stops at diplonema
89
When does oogenesis resume and what is completed?
resumes in puberty and completes the first meiotic division forming secondary oocyte and first polar body
90
Why is meiosis important?
re-shuffles genetic material and enhances genetic variation
