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Cell Biology > Mitosis and meiosis > Flashcards

Mitosis and meiosis Flashcards

1
Q

what is the main function of the cell cycle?

A

duplicate DNA in chromosomes and segregate the DNA into genetically identical daughter cells

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2
Q

when does the interphase occur?

A

phase between two successive M phases

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3
Q

describe the G1 phase;

A

growth phase

increased metabolic / biosynthetic activity

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4
Q

in G1 phase what 3 options does a cell have?

A
  • to continue cell cycle and enter S phase
  • stop cell cycle and enter G0 phase for undergoing differentiation
  • become arrested in G1 phase hence it may enter G1 phase or re-enter cell cycle
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5
Q

describe the S phase;

A

starts when DNA synthesis/replication commences

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6
Q

what does base pairing enable?

A

DNA replication

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7
Q

what does the semi-conservative DNA replication create?

A

two complete DNA double helices from the original molecule
- each parent strand serves as a template
- each new double helix has one of the original old strand

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8
Q

what is the double helix unwound by?

A

a helicase and topoisomerase

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9
Q

what is the process of DNA polymerase in DNA replication?

A

one DNA polymerase produces the leading strand copy

another binds to the lagging strand

this enzyme makes discontinuous segments

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9
Q

what are okazaki fragments?

A

discontinous segments, DNA ligase joins them together

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10
Q

when does the S phase occur?

A

when DNA synthesis commences

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11
Q

when does G2 phase occur?

A

occurs after DNA replication and is a period of protein synthesis and rapid cell growth to prepare the cell for mitosis

cells must be checked at the G2 checkpoint for any DNA damage within the chromosomes

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12
Q

what does the M phase consist of?

A

nuclear division (karyokinesis)

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13
Q

what is mitosis?

A

part of the cell in which replicated chromosomes are separated into two new nuclei

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14
Q

describe prophase in mitosis;

A

cell prepares to divide by tightly condensing its chromosomes and initiating mitotic spindle formation

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15
Q

what happens gene transcription during prophase?

A

it ceases, and does not return until late anaphase to early G1 phase

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16
Q

what is the centrosome?

A

the coordinating centre for the cells microtubules

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17
Q

what does phosphorylation of nuclear lamins cause?

A

the nuclear envelope to disintegrate into small membrane vesicles

microtubules invade the nuclear space

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18
Q

in late prometaphase what occurs?

A

kinetochore microtubules begin to search for and attach to chromosomal kinetochores

19
Q

what occurs when the microtubules have located and attached to the kinetochores in prometaphase?

A

the two centrosomes begin pulling the chromosomes towards opposite ends of the cell

20
Q

what does the metaphase checkpoint guarantees?

A

that kinetochores are properly attached to the mitotic spindle and that the chromosomes are aligned along the metaphase plate

21
Q

shortening of the kinetochore microtubules cause?

A

pulls the newly formed daughter chromosomes to opposite ends of the cell

22
Q

what happens when the polar microtubules push against each other?

A

causing the cell to elongate

23
Q

what occurs in the late anaphase?

A

chromosomes also reach their overall maximal condensation level

24
Q

what does each daughter cell have?

A

a complete copy of the genome of its parent cell

24
Q

outline what the role of telophase is in mitosis?

A

reversal of prophase and prometaphase events

24
Q

what happens in the telophase phase of mitosis?

A
  • polar microtubules lengthen
  • new nuclear envelope forms using membrane vesicles of parent cells old nuclear envelope

-new envelope forms around each set of separated daughter chromosomes

  • both sets of chromosomes begin to relax/decondense

-mitosis is complete

25
Q

describe what cytokinesis is?

A

cleavage furrow (pinch) containing a contractile ring, develops where the metaphase plate used to be, pinching off the separated nuclei

26
Q

what does the end of cytokinesis mark?

A

the end of the M phase

27
Q

what is meiosis?

A

cell division of germ cells in sexually-reproducing organisms that produces the gametes, eg-sperm/egg cells

28
Q

what happens prior to division of meiosis?

A

genetic material from the paternal and maternal copies of each chromosome is crossed over, creating new combinations of code on each chromosome

28
Q

what happens during fertilisation?

A

the haploid cells produced by meiosis from a male and female will fuse to create a cell with 2 copies of each chromosome again, the zygote

28
Q

how does meiosis occur?

A

involves 2 rounds of division = 4 cells with 1 copy of each chromosome (haploid)

28
Q

meiosis is divided into;

A

meiosis I & meiosis II

are further divided into karyokinesis I and cytokinesis I and karyokinesis II and cytokinesis II

29
Q

meiosis I and II are each divided into;

A
  • prophase
    -metaphase
  • anaphase
    -telophase
30
Q

what is prophase 1?

A

homologous maternal and paternal chromosomes pair, synapse and exchange genetic information, forming at least one crossover per chromosome

31
Q

what 4 series of substages is prophase I divided into?

A

1- leptotene
2-zygotene
3-pachytene
4-diplotene

32
Q

what is diakinesis?

A

nuclear membrane disintegrates into vesicles, and the meiotic spindle begins to form

33
Q

describe what happens in metaphase 1?

A

homologous pairs move together along the metaphase plate

33
Q

what occurs in anaphase 1?

A

kinetochore microtubules shorten, pulling homologous chromosomes to opposite poles

non kinetochore microtubules lengthen, pushing the centrosomes farther apart

33
Q

what happens the daughter cells in meiosis I?

A

each daughter cell now has half the number of chromosomes but each chromosome consists of a pair of chromatids

34
Q

when does the first meiotic division end?

A

when the chromosomes arrive at the poles

35
Q

what does pinching of the cell membrane cause?

A

two daughter cells

36
Q

what is resulted when cytokinesis does not fully complete?

A

cytoplasmic bridges - enables the cytoplasm to be shared between daughter cells until the end of meiosis II

37
Q

describe what prophase II is?

A

disappearance of the nucleoli and the nuclear envelope again, shortening and thickening of the chromatids

38
Q

what do centromeres contan?

A

two kinetochores that attach to spindle fibres from the centrosomes at opposite poles

39
Q
A

Cell Biology (30 decks)

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