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AS Biology > Cell division, mitosis and meiosis > Flashcards

Cell division, mitosis and meiosis Flashcards

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1
Q

Does the cell cycle take a long time?

A

Yes and it’s length depends on the type of cell

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2
Q

What happens in mitosis cell division?

A

One cell splits into 2 cells

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3
Q

Is mitosis just one part of a much longer process called the cell cycle?

A

Yes

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4
Q

How long can the cell cycle take in certain mammalian cells?

A

24 hours

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5
Q

What are the 2 main parts of the cell cycle?

A

The m phase (mitotic phase) and interphase

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6
Q

Does mitosis take place in the m phase?

A

Yes

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7
Q

Is the m phase only a short part of the cell cycle?

A

Yes

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8
Q

What does most of the cell cycle consist of?

A

Interphase

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9
Q
A
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10
Q

What are the 3 stages of interphase?

A
  • G1 phase
  • The s phase
    -The G2 phase
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11
Q

What happens during the g1 phase? (Interphase)

A

-The cell replicates organelles such as mitochondria

-Lots of transcription and translation takes place because replicating organelles requires a lot of proteins

  • The size of the cell increases to ensure that when the cell divides, the 2 daughter cells are the correct size
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12
Q

What happens in the s phase (synthesis)? (Interphase) use

A

-The chromosomes are replicated

-DNA synthesis

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13
Q

What happens in the G2 phase? (Interphase)

A
  • The cell replaces the energy stores used during the s phase
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14
Q

U

A

U

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15
Q

What happens in the m phase (mitotic phase)?

A

Mitosis and cytokinesis

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16
Q

What happens in mitosis?

A

Chromosomes separate into 2 nuclei

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17
Q

What happens in cytokinesis?

A

Cell divide into 2

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18
Q

What is G0 phase?

A

Where the cell exits the cell cycle. They enter G0 either because :

-Their fully differentiated e.g. neurones in adults

  • They’re senescent cells because their DNA is damaged

-Some cells enter temporarily e.g b memory cells

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19
Q

What happens if a cell fails a checkpoint?

A

It will leave the cell cycle and enter G0

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20
Q

What are the 3 checkpoints in the cell cycle?

A
  • The G1 checkpoint, where the cell checks that it’s grown to the correct size and checks for DNA damage.
  • The G2 checkpoint before the cell enters into the mitotic phase, the cell checks for DNA damage and that the cell has grown to the correct size
  • The metaphase checkpoint/spindle checkpoint, this checks that the chromosomes are assmebled correctly on the mitotic spindle. If this is the case, gen the cell finishes the cell cycle and proceeds to cytokinesis
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21
Q

What happens at the G1 checkpoint?

A

the cell checks that it’s grown to the correct size and checks for DNA damage.

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22
Q

What happens at the G2 checkpoint?

A

the cell checks for DNA damage and that the cell has grown to the correct size (right before mitosis)

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23
Q

What happens at the metaphase checkpoint?

A

this checks that the chromosomes are assembled correctly on the mitotic spindle. If this is the case, then the cell finishes the cell cycle and proceeds to cytokinesis

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24
Q

How many pairs of chromosomes do humans have?

A

23

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25
Q

When cells contain chromosomes in pairs what do scientists rder to them as?

A

Diploid cells

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26
Q

In cell division by mitosis, we start with one diploid cell nd end up with 2 diploid cells. Is this true?

A

Yes

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27
Q

Does cell division by mitosis produce 2identical copies of a cell?

A

Yes

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28
Q

Is mitosis used for asexual reproduction?

A

Yes

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29
Q

Mitosis specifically refers to the division of the nucleus. Is this correct?

A

Yes

30
Q

Do both mitosis and cytokinesis take place during the m phase of the cell cycle?

A

Yes

31
Q

Why can’t chromosomes in the nucleus he seen in interphase?

A

Because their not visible as distinct structures. Instead you see a dark material called chromatin

32
Q

In chromatin, the chromosomes have a loose open structure. Meaning that the DNA is accessible for transcription and replication.Is this true ?

A

Yes

33
Q

What are the 4 stages in mitosis?

A

Prophase, metaphase, anaphase and telophase

34
Q

What is the first stage of mitosis?

A

Prophase

35
Q

What happens in prophase, the first stage of mitosis?

A
  • The chromosomes condense and become visible in the nucleus. Each chromosome consists of 2 sister chromatids joined at the centromere.
  • The nucleolus disappears and the nuclear membrane starts to break down.

-A pair of centrioles move to either side of the cell

-Proteins begin to form spindle fibres which attach to the centromere of each chromosome. These spindle fibres start to move the chromosomes towards the centre of the cell.

36
Q

What happens in metaphase, the second stage of mitosis?

A
  • The spindle apparatus has completely formed and the and the chromosomes are limed up at the centre of the cell

-

37
Q

What happens in anaphase, the 3rd stage of mitosis?

A
  • The centromeres divide into 2 and the spindle fibres begin to shorten.
  • This pulls the sister chromatids to opposite poles of the cell
38
Q

What happens in telophase, the 4th stage of mitosis?

A

-The chromatids have reached the poles of the cells and they are now chromosomes again.

  • The spindle apparatus breaks down and the nuclear membranes reform

-The chromosomes uncoil back to their chromatin state and the nucleolus also reappears in each nucleus.

  • Mitosis is now complete and the cell is now ready to start cytokinesis
39
Q

What happens during cytokinesis?

A

-The central cell membrane is pulled inwards by the cytoskeleton. This creates a groove which gradually deepens.

-Eventually, the membrane’s fuse to form 2 independent cells.

40
Q

do centrioles play a role in forming the spindle apparatus in plant cells?

A

No because plant cells do not contain centrioles

41
Q

When plant cells undergo cytokinesis, can the cell membrane form a groove like in animal cells?

A

No, instead vesicles from the golgi apparatus form membrane structures down the centre of the cell

42
Q

When plant cells undergo cytokinesis, can the cell membrane form a groove like in animal cells?

A

No, instead vesicles from the golgi apparatus form membrane structures down the centre of the cell. These then fuse together to form a central cell membrane dividing the cytoplasm into 2. A new cellulose cell wall also forms down the centre

43
Q

is mitosis seen when : an organism grows an repairs itself, when an organism undergoes asexual reproduction?

A

Yes

44
Q

does cell division in meiosis only take place in sex organs?

A

yes

45
Q

why does cell division by meiosis only ever take place in sex organs?

A

because it’s only ever used to produce gametes (sex cells)(sperm , eggs, pollen)

46
Q

what cell do we start with in cell division by meiosis?

A

a diploid cell

47
Q

what do you end up with after meiosis?

A

4 haploid gametes, which contain individual chromosomes not pairs

48
Q

are all the gametes made by meiosis genetically different?

A

yes

49
Q

do both chromosomes in a homologous pair have exactly the same genes?

A

yes, however different alleles can be inherited from each parent

50
Q

Are the meiosis gametes genetically different or genetically the same?

A

Genetically different

51
Q

What happens before the nucleus divides by meiosis?

A

All the chromosomes are replicated in interphase

52
Q

Describe the process of crossing over in meiosis

A

2 chromosomes in a homologous pair come together and the chromatids of the 2 chromosomes wrap around each other

53
Q

What is the point where the chromatids join called?

A

The chiasmata

54
Q

Can parts of the chromatid break off and exchange between the homologous chromosomes?

A

Yes

55
Q

How many rounds of division is their in meiosis?

A

2

56
Q

What are the 2 rounds of division in meiosis?

A

Meiosis 1 and meiosis 2

57
Q

In brief what happens in meiosis 1?

A

Homologous chromosomes are separated from each other

58
Q

In brief, what happens in meiosis 2?

A

Sister chromatids are separated from each other

59
Q

What happens before meiosis starts?

A

The cell undergoes interphase, where chromosomes and organelles are copied

60
Q

What is the first stage of meiosis 1?

A

Prophase 1

61
Q

What is the first stage of meiosis 1?

A

Prophase 1

62
Q

What happens in prophase 1 (the first stage of meiosis 1)?

A

-The chromosomes condense and become more visible

-Homologous chromosomes link together, forming the chiasmata

-Crossing over occurs and alleles are exchanged

-The nuclear membrane breaks down

-The centrioles move to opposite poles of the cell

-The spindle fibres start to assemble into the spindle apparatus

63
Q

What happens in metaphase 1 (the second stage of meiosis 1)?

A
  • Pairs of homologous chromosomes line up on the equator of the spindle apparatus
64
Q

What happens in anaphase 1 (the 3rd stage of meiosis 1)?

A

-Spindle fibres shorten and the chiasmata between homologous chromosomes break.

-This causes the chromosomes to move to opposite poles of the cell.

65
Q

What happens in telophase 1 (the 4th stage of meiosis 1)?

A

-Chromosomes have reached the poles of the cell and the nuclear membranes reform.

-The Chromosomes uncoil back to their chromatin state

-The cell undergoes cytokinesis

-2 haploid cells are produced and these no longer contain pairs of homologous chromosomes

66
Q

What are the stages of meiosis 2?

A

Prophase 2, metaphase 2 , anaphase 2 and telophase 2

67
Q

What happens in prohase 2? (The first stage of meiosis 2)

A

-The chromosomes condense and become visible again

-The nuclear membrane breaks down and the spindle fibres begin to develop

68
Q

What happens in metaphase 2 ? (The second stage of meiosis 2)

A

The chromosomes are lined up on the equator of the spindle apparatus

69
Q

what happens in anaphase 2 ?(The 3rd stage of meiosis 2)

A

-The centromere of each chromosome divides and the spindle fibres shorten

-Chromatids are now pulled towards opposite poles of the cell

70
Q

what happens in telophase2 ?(The 3rd stage of meiosis 2)?

A

-chromatids have reached the poles of the cell and have now become chromosomes

-nuclear membranes reform and the chromosomes uncoil back to their chromatin state

-cytokinesis occurs and 2 haploids are produced, 4 new cells in total

71
Q

what ensures genetic variation in meiosis?

A

crossing over and the assortment of chromosomes

AS Biology (15 decks)

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