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Cell Biology > Mitosis and the Mitotic Cell Cycle > Flashcards

Mitosis and the Mitotic Cell Cycle Flashcards

1
Q

In eukaryotes DNA is organised into …

A

…chromosomes

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2
Q

Chromosomes can be stained and examined using a…

A

…light microscope.

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3
Q

The chromosomes can be organised by size and shape into…

A

…a karyotype

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4
Q

Length of DNA in a human cell ?

A

2m

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5
Q

In humans there are usually two of each …

A

…chromosome (diploid 2C) in our somatic cells

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6
Q

In some stages of the life cycle of some organisms there is one copy of …

A

…each chromosome (haploid 1C).

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7
Q

Species with more than 2 copies of each chromosome are described as…

A

…polyploid

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7
Q

Most higher plants are …

A

…polyploid

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7
Q

Species with four copies of each chromosome are…

A

…tetraploid 4 C

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8
Q

In some species there are three copies …

A

…(triploid 3C)

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9
Q

The replication of DNA and its subsequent distribution into
two daughter cells is one of the most …

A

…fundamental processes
carried out in living organisms

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10
Q

Mitosis was first described by …

A

…Strasburger in 1880

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11
Q

Strasburger in 1880 divided mitosis into four phases:

A

1) prophase (in which the chromosomes become visible).
2) metaphase (where the chromosomes align at the
equator of the cell).
3) anaphase(where the two chromosome sets move to
opposite poles of the dividing cell).
4) telophase (where the new nuclear membranes are
formed and the chromosomes disappear).

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12
Q

Observations made by Eduard Strasburger in 1880 from a living plant cell in a…

A

…hair cell from a Tradescantia flower.

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13
Q

What occurs in the interphase?

A

The cell is carrying out its normal activities. It is not clear if the cell is in G1, S-phase or G2.

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14
Q

Cells in S-phase are …

A

…replicating their DNA

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15
Q

What occurs in Early Prophase?

A

The cell passes out of G2 Interphase and enters Mitosis (M-Phase).
Here, the nuclear membrane starts to degrade.
The nucleolus vanishes.
The Chromosomes condense to become Visible.

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16
Q

the chromosomes consist of…

A

…two chromatids

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17
Q

What occurs in Late Prophase?

A

The chromosomes continue to shorten and thicken. The spindle forms from the poles of the cell.

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18
Q

What occurs at Metaphase?

A

The spindle fibres attach to the chromosomes at
the Centromere (the Kinetochore within the
centromere). The chromosomes line up
along the equator of the cell.

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19
Q

Material which is dividing can be treated with …

A

…a mitotic poison such as colchicine (from the autumn crocus). This disrupts the metaphase.

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20
Q

At metaphase, how many chromatids are in each chromosome?

A

2

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21
Q

Treatment of dividing material during the metaphase with a mitotic poison, stops and disrupts the…

A

…spindle forming and the chromosomes are ‘liberated’.

  • Counting cells where this takes place can give an indication of the kinetics of the cell cycle and enable the cell doubling time to be determined.
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22
Q

What occurs in the Anaphase?

A
  • The chromatids
    separate at their
    centromeres
  • One chromatid from
    each of the chromosome moves to opposite poles of the cell.
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23
Q

What occurs in the Telophase?

A
  • The chromosomes de-condense (a reverse of prophase) forming two nuclei at the poles of the cell.
  • Each chromosome now consists of one DNA molecule (one chromatid).
  • The process is completed when cytokinesis forms two daughter cells. Each daughter cell passes into G1 of Interphase
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24
Q

What happens in Cytokinesis?

A

The two cells divide

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25
Q

The process of cytokinesis differs between…

A

…plants and animal cells

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26
Q

Why does cytokinesis differ in animal and plant cells?

A

Because animal cells do not have a cell wall

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27
Q

What are the functions of Mitosis?

A

1) Reproduction
2) Growth and development

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28
Q

Describe reproduction of an amoeba.

A

1) An amoeba
2) A single-celled eukaryote, is dividing into two cells.
3) Each new cell will be an individual organism

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29
Q

Describe growth and development following fertilization?

A

Sand dollar embryo shortly after the fertilized egg divided, forming two cells.

30
Q

Describe growth and development (tissue renewal).

A

Dividing bone marrow cells give rise to new blood cells.

31
Q

In 1953, Howard and Pelc recognised that the interphase of dividing cells of Vicia faba had …

A

… three phases

32
Q

Three phases of the interphase of
dividing cells?

A

i. pre-synthetic phase or G1
ii. DNA-synthetic phase or S-Phase
iii. post-synthetic phase or G2

33
Q

Cells in G2 subsequently enter …

A

…mitosis

34
Q

after division, the daughter cells enter…

35
Q

The term cell cycle refers to …

A

…the passage of cells in time from one division to the next, starting at M, proceeding to G1, on to S, then to G2, and finally to M again.

36
Q

What occurs during S- phase?

A
  • Synthesis of DNA
  • Each DNA molecule replicates
  • Centrioles divide
37
Q

Whats the C value?

A

Multiples of the haploid DNA amount throughout the diploid mitotic cell cycle.

38
Q

The term “cell cycle” suggests a continuous process, some
cells cease …

A

…cycling and enter a resting state known as G0

39
Q

During development it may be necessary for the cell cycle in a
population of cells to …

A

…cease, e.g. when a young leaf reaches
maturity cell division is no longer required.

40
Q

In plants the cell cycle may…

A

…re-start if wounding occurs

In animals this is a very rare event but does occur in the case of cancer.

41
Q

What method is used to measure the cell cycle?

A
  • Percentage labelled mitoses method
  • Cell culture method
42
Q

Percentage labelled mitoses method process?

A

Look at powerpoints

43
Q

Labelled mitosis as a percentage of …

A

…total mitoses counted using
light Microscopy of autoradiographs.

44
Q

The duration of the phases of the cell cycle can be calculated from…

A

… the results

45
Q

Cell Culture Method process?

A

Look at powerpoints

46
Q

The principal control point (PCP) hypothesis Van’t Hof and Kovacs (1972) (in Bryant and Francis, The Cell Division
Cycle in Plants) stated that …

A

…cell division in a complex tissue is
regulated by factors that operate during G1 and G2 and that under conditions where cell division ceases these factors become limiting, causing cell arrest in late G1 or G2.

47
Q

The PCP hypothesis was developed from …

A

…data derived from observations on root meristems. However, experiments indicated that cell division is also regulated the same way in shoot
apices.

48
Q

The Cell Culture Method is faster than…

A

… the Percentage labelled mitoses method.

49
Q

the two major checkpoints in the mitotic cell cycle control entry into which phases?

50
Q

Cell division genes (and the proteins they code) that control G1 and G2 of the cell cycle in yeast gave the first indications that …

A

…similar genes/proteins may operate in higher plants and animals.

51
Q

Two main areas of research have enabled …

A

…basic cell cycle control to be elucidated.

52
Q

What are the two main areas of research which enabled basic cell cycle
control to be elucidated?

A

1) Research into proteins regulating cell division in the sea urchin, clams and frog (Xenopus).
2) Research into the genetics of cell division in the fission yeast,
Schizosaccharomyces pombe, and the budding yeast, Saccharomyces cerevisiae.

53
Q

Two major types of proteins were found to be involved in the control of the cell cycle?

A

1) A kinase (an enzyme that adds phosphate groups to other proteins modifying protein activity).
2) A cyclin whose concentrations fluctuate, increasing prior to cell division and dropping after cell division

54
Q

A factor was isolated from Xenopus laevis eggs that induced …

A

…eggs to undergo premature meiosis and mature.

55
Q

The factor from Xenopus laevis eggs also affected mitosis and was found to …

A

…rise as the cells enters mitosis and drop following cell division.

56
Q

What was the factor from Xenopus laevis eggs named?

A

This substance was named
maturation promoting factor (MPF); similar substances were also
found in sea urchins and clams.

57
Q

the gene, cdc2, was discovered in …

A

…S. pombe
(fission yeast)

58
Q

the gene cdc2 is required at…

A

…two control points in the cell cycle, in late G1, and again, in G2 before mitosis

59
Q

In S. cerevisiae a gene with the same function, called CDC28, was discovered and it was found to be…

A

…homologous to the cdc2
gene of S.pombe

60
Q

The gene encoded by cdc2/CDC28 is a …

A

…34 kd kinase (called p34 kinase) the activity of which sends yeast cells into
mitosis.

61
Q

Other homologs to the cdc2 gene were found widely distributed in nature in …

A

…clams, Xenopus, humans and higher plants.

62
Q

The human p34 kinase was…

A

…62% homologous to cdc2 and
functionally equivalent to the yeast enzyme.

63
Q

MPF was found to be comprised of …

A

…two proteins with molecular
weights of 34,000 and 45,000.

64
Q

P34 is known as a …

A

…kinase (Cdk)

65
Q

P34 is known as a kinase because…

A

…it phosphorylates a
variety of target cell cycle proteins.

66
Q

P34 is activated by…

A

…phosphorylation at the critical control points in the cell cycle.

67
Q

The cyclin came to be known as …

A

…cyclin B, it regulates entry of
the cell into mitosis from G2.

68
Q

Cyclin D regulates …

A

…the entry of cells into S-Phase
so they can undergo DNA replication.

69
Q

Cyclin A, initiates …

A

…DNA replication in S-phase

70
Q

cell cycle control is similar in …

A

…most eukaryotic organisms.

71
Q

p34 like cyclins are well …

A

…conserved throughout nature as are many of the other cell cycle control genes/proteins

72
Q

Whats Cdk?

73
Q

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