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MGD > Lecture 1.2 Mitosis, Meiosis and DNA replication > Flashcards

Lecture 1.2 Mitosis, Meiosis and DNA replication Flashcards

1
Q

what are the stages of the cell cycle?

A

G0, G1, S phase, G2, cell division

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2
Q

what happens in G1 phase?

A

the cell content replicates

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3
Q

when is the cell cycle checkpoint?

A

after G1

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4
Q

what is the role of the cell cycle checkpoint?

A

to check if G1 is complete and signifies to the cell if it can move to S phase. once has the appropriate signals, enters S phase

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5
Q

what happens in S phase?

A

DNA replicates

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6
Q

what happens in G2 phase?

A

there is double of everything in cell (content & DNA)

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7
Q

where is the second cell checkpoint?

A

in G2 phase

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8
Q

what is the role of the second cell checkpoint?

A

to check the duplicated DNA is perfect and there aren’t any mutations, if there are mutations, a repair mechanism goes underway. also signals the cell that everything has been replicated and the DNA and chromosomes are fully intact before it enters cell division

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9
Q

what is DNA replication?

A

when the existing DNA template is used to produce 2 new double stranded DNA molecules

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10
Q

describe DNA replication, generally.

A

the existing strands break apart and each strand is a parent strand for the synthesis of a new complementary strand

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11
Q

what is the equation for DNA replication?

A

(dNMP)n + dNTP -> (dNMP)n+1 + PPi

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12
Q

what is the direction the new strand gets built?

A

5’ to 3’

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13
Q

what type of reaction is DNA replication? (timing)

A

stepwise reaction (one at a time)

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14
Q

what are the 3 stages of DNA replication?

A

initiation, elongation, termination

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15
Q

what happens in the first phase of DNA replication (intitiation)?

A

an enzyme called helicase unwinds and separates the double-stranded DNA by breaking the hydrogen bonds between base pairs. single stranded binding proteins bind to the single strands to stop the reforming of helix. enzyme called primase binds to the leading strand of DNA and creates a complementary piece of DNA attached to the template at the 3’ end

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16
Q

what happens in the second stage of DNA replication (elongation)?

A

primase is removed and DNA polymerase adds multiple nucleotides to 3’ end of the polynucleotide that’s added by the DNA primase, to create a new DNA structure, therefore have a continuous strand of DNA replication. the other (lagging) strand of the helix runs in the opposite direction, therefore cannot have a continuous strand of production. primase sits at various points along the template, creating small fragments of DNA (Okazaki fragments). the Okazaki fragments are put together by an enzyme called ligase.

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17
Q

why does one strand have a discontinuous production of a new strand?

A

because DNA polymerase only works in the 5’ to 3’ direction

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18
Q

what happens in the last stage of replication (termination)?

A

2 new helix’s are produced so there are 2 old strands and 2 new strands have been created

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19
Q

how do anti-cancer drugs affect replication?

A

they inhibit elongation and termination of DNA sequencing

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20
Q

what anti-cancer drugs inhibit elongation of replication?

A

BCNU and cisplatin - used to treat metastatic testicular cancer and leukemia

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21
Q

what anti-cancer drugs inhibit termination of replication?

A

AraC and 6-MP - used to treat acute leukaemia

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22
Q

what is the outcome of DNA replication?

A

there is double the amount of DNA but it is combined by a centromere. each chromosome = 2 chromatid. one chromosome = 2 DNA molecules. both are identical DNA molecules

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23
Q

what are the 3 locations for the centromere called?

A

metacentric, submetacentric, acrocentric

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24
Q

what is the location of the centromere that doesn’t exist in humans?

A

telocentric

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25
Q

how to the chromosomes vary in centromere locations?

A

different number of chromosome has a different centromere location

26
Q

what is a telomere?

A

caps at the ends of each strand of DNA to protect the chromosomes.

27
Q

what is mitosis?

A

the separation of a single cell into 2 identical daughter cells (2 diploid cells), which have the same chromosome content as the parental cells, and occurs within somatic cells

28
Q

what are somatic cells?

A

any cell in the body except the sperm and egg cell

29
Q

give 2 examples of how mitotic growth is necessary for human tissue.

A
  1. epidermis (top layer of skin): accumulation of dead cells + dead cells moving up the layers bcs of mitotic growth of cells in the lower layers
  2. creating more wbc and rbc in bone marrow through mitotic divisions
30
Q

what are the stages of mitosis?

A

PpMAT (G2, prophase, prometaphase, metaphase, anaphase, telophase, cytokinesis)

31
Q

what happens during prophase?

A

nuclear envelope begins to dissolve, there are still free floating chromosomes, the spindle fibers begin to form but aren’t yet attached to chromosomes.

32
Q

what happens during prometaphase?

A

spindle fibers being to attach to the centromere of the individual chromosomes

33
Q

what happens during metaphase?

A

chromosomes line up across the equator of the cell with spindle fibers attached to centromeres and the poles.

34
Q

what happens during anaphase?

A

spindle fibers contract, pulling each of the chromatids to the opposite ends of the cell, resulting in the DNA becoming a single DNA molecule, cleavage furrow has begun for form

35
Q

what happens during telophase?

A

the cleave furrow forms and beginning of 2 cells occurring and 2 nuclear membranes form. cytokinesis happens (1 cell separates into 2 cells) and each individual daughter cell enters G1.

36
Q

where does meiosis occur?

A

in specialized germ cells to form egg and sperm cells

37
Q

what does meiosis produce?

A

4 non-identical daughter cells with half the chromosome number than the parental cells, so 4 haploid cells

38
Q

how many stages of meiosis are there?

A

2

39
Q

what happens in prophase 1 of meiosis?

A

disintegration of nuclear membrane, chromosomes condense, chromosomes pair up to form bivalents and synapsis takes place to form a tetrad, crossing over occurs at the chiasma, these chromosomes line up at the equator, nuclear membrane fragmenting

40
Q

what happens in metaphase 1 of meiosis?

A

spindle fibers form and attach to the centromeres of the tetrad

41
Q

what happens in anaphase 1 of meiosis?

A

chromosomes are pulled apart by the spindle fibers to the opposite poles of the cell

42
Q

what happens in telophase 1 of meiosis?

A

in each cell you have half the amount of chromosomes as the parental cell, the nuclear membrane reforms and cytokinesis takes place, producing 2 haploid cells

43
Q

what happens in the second division of meiosis?

A

splits 2 chromatids on each chromosome so that each daughter cell has 1 chromatid per chromosome

44
Q

what happens in prophase 2 of meiosis?

A

chromosomes condence, nuclear membrane dissolved and spindle fibers reappear

45
Q

what happens in metaphase 2 of meiosis?

A

chromosomes line up at the equator and spindle fibers attach to the centromere

46
Q

what happens in anaphase 2 of meiosis?

A

centromeres separate and chromatids of each chromosome separate and move to each end of the cell. end up with cells containing 1 copy of chromosome, not 2

47
Q

what are the 4 consequences of meiosis?

A

create germ cells, create process of genetic diversity, crossing over of genetic material, random assortment of chromosomes

48
Q

what does meiosis essentially allow?

A

maintain a constant chromosome number through generations and promote genetic diversity

49
Q

what is spermatogenesis?

A

cell division to produce male gametes

50
Q

what is the process of spermatogenesis?

A

particular cell types (spermatogonium) undergo mitosis to form a primary spermatocyte. this undergoes meiosis to create 4 spermatids which mature into sperm.

51
Q

what is the difference between spermatogonium and primary spermatocyte?

A

the genes expressed

52
Q

what does spermatogenesis produce?

A

1 spermatocyte (2n) produces 4 sperm (n)

53
Q

how long does it take for spermatogenesis to take place?

A

approx 48 days

54
Q

what is oogenesis?

A

cell division to produce female gametes

55
Q

what is the process of oogenesis?

A

original cell (oogonium) undergoes mitosis and differentiates to produce primary oocyte, meiosis occurs to produce 4 daughter cells, only 1 egg is produced from the 4 daughter cells and 3 polar bodies

56
Q

what is the length of oogenesis?

A

12-50 years. oogenesis only happens from puberty onwards. oocytes are produced in the formation of the fetus but egg cells are created from puberty onwards.

57
Q

what is missegregation?

A

chromosomes going in the wrong place

58
Q

what are 4 reasons why are clinicians interested in meiosis?

A
  1. many severe consequences of faulty meiosis
  2. 1/3 all identified miscarriages
  3. infertility
  4. leading cause of mental retardation
59
Q

what are 3 reasons why are clinicians interested in mitosis?

A
  1. regeneration of tissues
  2. manipulation of stem cells
  3. cancer and neoplasm (expansion of cells) biology and therapeutics
60
Q

what are 7 differences/similarities between mitosis and meiosis?

A
  1. mitosis 1 division, meiosis 2
  2. mitosis no synapsis, meiosis yes (form bivalents)
  3. mitosis no crossing over, meiosis yes (p1)
  4. mitosis prod 2 cells, meiosis prod 4 cells
  5. mitosis prod diploid, meiosis prod haploid
  6. mitosis happen body cells, meiosis happen gamete
  7. mitosis prod identical cells, meiosis prod variation
61
Q

what happens in telophase 2?

A

the chromosomes reach opposite poles, the nuclear envelope reforms, cytokinesis occurs and the 2 cells produced by meiosis 1, prod 4 haploid cells.

MGD (2 decks)

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