module 2 - 6.2 mitosis Flashcards

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1
Q

what does the nucleus contain?

A

chromosomes but as chromatin

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2
Q

what is chromatin?

A

a tangle of unwound chromosomes (DNA) to allow genes to be expressed (e.g. protein synthesis)

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3
Q

when is the DNA unwound?

A

during proteins synthesis

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4
Q

what is a chromosome?

A

a molecule of DNA (linear molecule)

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5
Q

what is a centromere made of?

A

protein

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6
Q

why are the chromosomes packaged?

A

so they can be moved in mitosis

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7
Q

what are the chromatids called when they are joined together in one chromosome?

A

sister chromatids

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8
Q

how are there 2 chromatids in the chromosome?

A

1 line is the original chromosome, the second is its copy of chromosome

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9
Q

what are centromeres drawn as when they are drawn more realistically?

A

2 protein complexes

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10
Q

how do you work out the number of chromosomes?

A

count the number of centromeres (when not draw as individual proteins, only as blobs)

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11
Q

what are the stages of mitosis?

A

prophase
metaphase
anaphase
telophase

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12
Q

what happens before prophase?

A

chromosomes have been replicated/ synthesised during the S phase

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13
Q

what are the chromosomes as a diploid number?

A

2n = 4

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14
Q

what are the chromosomes as a haploid number?

A

n = 2 (1 long chromosome, 1 short chromosome)

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15
Q

what does the n stand for in the haploid number of chromosomes?

A

n = number of different chromosomes based on length/ position of centromere/ bonds

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16
Q

what happens during early prophase?

A
  1. chromosomes replicated and condensed, exist as pair of sister chromatids held by centromeres
  2. centrioles begin to produce spindle fibres, one centriole moves to opposite pole
  3. nuclear envelope begins to disappear
  4. spindle fibres grow and bind to centromeres so they can move chromosomes around
17
Q

how is the movement of centrioles special?

A

movement of centrioles happens in ALL ANIMALS but only in SOME PLANTS

18
Q

what happens during late prophase?

A
  1. nuclear envelope nearly digested/disappeared
  2. spindle fibres bind to centromeres and start to move chromosomes around ready for metaphase checkpoint
19
Q

what happens during metaphase and the metaphase checkpoint?

A
  1. spindle fibres move the chromosomes so
    they line up on equator of cell called METAPHASE PLATE (meet in the middle)
  2. cell only proceeds to anaphase if conditions of metaphase checkpoint are met
20
Q

what are the conditions of the metaphase checkpoint that need to be met?

A
  • all chromosomes attached to a spindle fibre
  • all chromosomes on the metaphase plate
21
Q

what happens during anaphase?

A
  1. spindle fibres contract and pull apart sister chromatids, so they’re called chromosomes again
  2. chromosomes pulled to poles of the cell, the ‘arms’ of each chromosome trail behind as they are pulled through the cytoplasm
22
Q

what happens during telophase?

A
  • start of cleavage furrow
  • cytoskeleton begins to separate the cytoplasm and pull into plasma membrane
  • cell still a single cell but with 2 nuclei, cell nucleus is a copy of original cells
  • mitosis is finished
23
Q

what is cytokinesis?

A

last stage of ‘mitotic phase’

24
Q

what happens during cytokinesis within animal cells?

A
  • cytoskeleton pulls the plasma membrane into the cleavage furrow
  • cells separate forming 2 daughter cells
  • chromosomes unpackage to form CHROMATIN
  • cell enters G1
25
Q

what happens during cytokinesis in plants?

A
  • vesicles line up on metaphase plate and fuse to form 2 separate plasma membranes
  • on cell plates, cell wall forms for EACH cell so 2 cell walls form
  • 2 daughter cells will grow during G1