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BIOSCI 107 > L10 - Cell Division > Flashcards

L10 - Cell Division Flashcards

1
Q

Cell destinies

A

1) live and function without dividing
2) grow and divide
3) die
Various signals tell a cell which path to take

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2
Q

Homeostasis maintenance

A

Balance between cell proliferation and death

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3
Q

Cell division frequency by cell type

A

Skin, blood, liver cells divide frequently

Brain, nerve and muscle cells don’t divide after maturing

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4
Q

G1

A

normal cell processes + some prep for division

  • most cellular activities (metabolically active cell)
  • duration variable (cell type specific)
  • organelle/cytoplasm component duplication
  • Centrosome replication begins
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5
Q

S

A

DNA replication
- Strands separate at H bonds holding nucleotides together
- New strand of DNA synthesised opposite each old strand
- Catalysed by DNA polymerase
- Proofreading (careful process)
S onwards is mostly prep for cell division

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6
Q

G2

A
  • cell growth continues
  • checks for correct DNA synthesis
  • prepares for mitotic phase (synthesis of required proteins, enzymes, gather reactants)
  • Centrosome replication complete
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7
Q

G0

A
  • exit from cell cycle
  • become non-dividing cells (e.g most nerve cells)
  • cells held so they don’t proceed through rest of cycle
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8
Q

Mitosis prophase

A
  • DNA condenses further
  • mitotic spindles (microtubules) form
  • two identical chromatids (sister chromatids) per chromosome
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9
Q

Mitosis prometaphase/late prophase

A
  • nuclear membrane fragments
  • kinetochore microtubules attach to kinetochore of chromosome
  • chromosomes condensed
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10
Q

Mitosis metaphase

A
  • individual chromosomes line up at centre (metaphase plate)

- centrosomes are at each cell pole

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11
Q

Mitosis anaphase

A
  • sister chromatids separated and pulled to opposite cell poles by spindle fibres
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12
Q

Mitosis telophase

A
  • nuclear envelope reforms

- spindle fibres disappear

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13
Q

Chromosome numbering

A

Longest is 1

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14
Q

Homologous chromosomes

A

One maternal one paternal, same genes

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15
Q

Sister chromatids

A

Identical, result of DNA replication

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16
Q

Non-sister chromatids

A

Sister chromatids of each homologous chromosome

17
Q

Centromere

A

One on each chromatid

18
Q

Sister chromatid cohesion

A

Several attachment points that keep sister chromatids together

19
Q

Mitotic cell cycle checkpoints

A

G1 checkpoint, G2 checkpoint, M checkpoint

20
Q

G1/S transition

A 
Checks cell conditions for S phase
- DNA undamaged?
- health/quality of cells (size/nutrition)
- sufficient organelles
- appropriate signals present?
If standards not met, cell enters G0
21
Q

M checkpoint (prior to completion of mitosis)

A
  • are all chromosomes attached to spindles
  • inappropriate complement of chromosomes = apoptosis (cell dies instead of contributing to associated tissue/organ incorrectly - better for the organism)
22
Q

Key proteins involved in checkpoints

A
  • cyclin and CDK (cyclic changes work as mitosis clock, controls by phosphorylating other proteins)
  • MPK
  • external signals (e.g growth factors): control via signalling transduction pathways
23
Q

Meiosis prophase 1

A
  • synapsis to form tetrads, crossing over
24
Q

Synapsis

A

Two sister chromatids of each pair of homologous chromosomes (non-sister chromatids) pair up

25
Q

Tetrad

A

4 chromatids paired from synapsis

26
Q

Crossing over

A

Non-sister chromatids within tetrads cross over at chiasmata

- results in genetic recombination

27
Q

Meiosis metaphase 1

A

Homologous chromosomes pairs line up in centre

- independent assortment

28
Q

Meiosis anaphase 1

A

Homologous chromosomes separated to each cell pole

- Sister chromatids remain attached

29
Q

Meiosis 2

A

Similar to mitosis

30
Q

Sources of variation in meiosis

A

Independent assortment, crossing over, gamete fusion

31
Q

no. chromosomes and chromatids after meiosis 1 and 2

A 
both result in haploid
meiosis 1:
- 23 chromosomes
- 46 chromatids
meiosis 2:
- 23 chromosomes
- 23 chromatids
1 chromosome refers to both when there is 1 chromatid only and when there is a pair of sister chromatids

BIOSCI 107 (15 decks)

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