cell division Flashcards

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1
Q

what are the 3 phases interphase is split into

A

G1, S, G2

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2
Q

what occurs at interphase G1?

A
  • growth phase
  • preparations (duplicating organelles, growing in size & making proteins) are made to ensure the cell is ready to go into S phase
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3
Q

what occurs in S and G2 phase

A

S phase::
-now no going back
-also called the synthesis phase because this is where DNA synthesis occurs
- DNA replicates- more important sequences are replicated first.
-each chromosome consist of a pair of sister chromatids
G2 phase::
-cell grows in prep for mitosis

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4
Q

where does exiting of the cell cycle occur

A
  • occurs early in G1 phase- cells can either continue in the cell cycle or enter the G0 phase (exiting the cell cycle)
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5
Q

what do cells do in the G0 phase

A
  • cells in the G0 phase may differentiate, die or enter senescence (where they stop dividing)
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6
Q

in what part of the cell cycle is DNA replicated

A

the S phase

… the G2 phase is where the cell is getting prepared to double

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7
Q

what are the 3 things mitosis is used for?

A

growth, tissue repair, wound repair

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8
Q

why is mitosis relevant for tissue repair?

A
  • mitosis can produce a genetically identical copy.

- the new cell is able to take over the cell that was lost as it contains all the same genes- e.g repair of skin

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9
Q

why is mitosis relevant for wound repair

A

a wound stimulates the action of white blood cells, platelets and growth factors.
these cause cells to undergo mitosis to repair damaged tissues/ blood vessels
- ensures for fast wound recovery

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10
Q

why is mitosis relevant for growth

A
  • allows for a growth of a foetus, cells duplicate

- all multicellular organisms grow by producing genetically identical cells

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11
Q

what do bacteria reproduce asexually by?

A

via binary fission

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12
Q

what type of offspring does asexual reproduction result in?

A

genetically identical offspring

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13
Q

when can damage to DNA occur

A

during DNA replication in interphase (s phase)

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14
Q

why is the DNA replication phase ( S phase) kept short

A

since exposed bases are more susceptible to mutation

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15
Q

what do cell cycle checkpoints do?

A
  • when mutation occurs damaged DNA id detected and repaired
  • makes sure DNA is replicated once in each cycle
  • also checks cell division and that its not going too fast as tumours and cancer can then form
  • ensures the cell cycle goes in one direction or sections could occur twice
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16
Q

what are cell checkpoints

A

-times in the cell cycle where chemical events occur to regulate division

17
Q

what happens at the G1/S checkpoint (restriction point)

A

during the G1 phase a chemical can trigger a cell to leave the cell cycle and enter G0- makes sure there are not too many cells or not too few cells

18
Q

what happens at the G1 checkpoint

A

checks cell is ready for S phase ( occurs at the end of G1)

19
Q

what happens at the G2/M checkpoint

A
  • checks and repairs DNA

- makes sure all the DNA has been checked and repaired before the cell enters mitosis

20
Q

what happens at the mitosis checkpoint

A
  • checkpoint in the middle of mitosis

- checks cell is ready to proceed in mitosis

21
Q

what can happen when the genes controlling cell division mutate

A

-cell division can occur uncontrollably

22
Q

whats a chromosome

A

a set of genes made from chromatin (genetic material) wrapped around histones

23
Q

where do spindle fibres attach and what do they do

A

at the centromere and separate the chromosomes

24
Q

whats a chromatid

A

a copy of a chromosome while attached to a duplicate

25
Q

how many chromosomes does a human (somatic (body)) cell contain

A

46 chromosomes ( 23 pairs of homologous chromosomes)

26
Q

what does each pair of chromosomes contain

A

one chromosome from each parent

27
Q

what are many body cells ( haploid or diploid)

A

diploid

28
Q

what are homologous chromosomes

A

matching pairs of chromosomes ( 1 paternal 1 maternal) containing the same genes at the same place but may contain different alleles (variants for the gene)

29
Q

what occurs in meiosis one: prophase 1

A
  • nuclear envelope disappears
  • homologous chromosomes pair up and chromatids cross over==-crossing over- random chromatin moves from one pair to another (genes will change)
30
Q

what occurs in meiosis one: metaphase 1

A
  • spindle fibres form and reach chromosomes
  • pairs of chromosomes line up on the equator
  • pairs line up in a random order (paternal and maternal each way)
  • this is independent assortment
31
Q

what occurs in meiosis one: anaphase 1

A
  • entire chromosomes=pulled to poles

- homologous pairs= now separated

32
Q

what occurs in meiosis one: telophase 1

A
  • two nuclei reform
  • each is haploid
  • chromosomes decondense
  • cytokinesis follows
33
Q

what occurs in meiosis two: prophase 2

A
  • nuclear envelope disappears
  • chromosomes condense
  • chromosomes move to poles +s.f form
34
Q

what occurs in meiosis two: metaphase 2

A
  • chromosomes line up in single file at equator
  • s.f binds to centromeres
  • random arrangement introduces further variation
35
Q

what occurs in meiosis two: anaphase 2

A

-chromatids= separated and are pulled to poles

36
Q

what occurs in meiosis two: telophase 2

A
  • envelope forms
  • chromosomes decondense
  • cytokinesis splits to produce 4 haploid cells
37
Q

where is variation introduced in sexual reproduction

A

-crossing over in prophase 1, independent assortment in metaphase 1, random arrangement in metaphase 2, random selection of gametes that fuse