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Cell Biology > Cell Cycle And Meiosis > Flashcards

Cell Cycle And Meiosis Flashcards

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1
Q

What is another word for mitosis

A

Somatic cell division (non reproductive)

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2
Q

How many phases does the cell cycle have and name them

A

4

M phase
G1
S
G2

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3
Q

Explain all 5 stages of M phase (mitosis to cytokinesis)

A

Prophase - mitotic spindles form from centrosomes
Chromosomes condense

Prometaphase -
Nuclear membrane breaks down
Sister chromatids have formed
Kinetichore microtubules attach

Metaphase-
Chromosomes align on equator
Kinetochore microtubules contract
Centrosomes are at spindle poles

Anaphase -
Split sister chromatids move to spindle poles
Microtubules shorten

Telophase -
Nuclear envelope reassembles around sets
Contractile rings start to contract

Cytokinesis -
Contractile rings (with actin) contract and create cleavage (split cells)
Chromosomes become deconstructed again
Microtubules form again at centrosomes

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4
Q

What is another word for centromere on chromatids which binds to microtubules

A

Kinetochore

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5
Q

What are contractile rings and function

A

They contract and actin is involved

This cleaves the cell and split cells in mitosis

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6
Q

Explain the 3 phases briefly of interphase

A

G1- prepare cell for dna synthesis
Doubles the organelles
Synthesise proteins for dna replication

S- dna replication

G2- prepare cell for mitosis
Synthesise proteins for mitosis

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7
Q

Where are the main checkpoints

A

G1 + G2

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8
Q

Name the signals/ regulation of checkpoints that show cell is either ready or not

A

Growth factor proteins

Density optimal of the cell (whether cell is next to others)

Anchorage dependency - cells need to be anchored to others for division

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9
Q

What do the check points look out for in G1 G2 and M phase

A

G1- whether cell is big enough
If environment is favoured
If dna is damaged (would stop replication)

G2- check dna is replicated and correct
Check environment is favoured

M phase- check all chromatids attached to spindle

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10
Q

Explain the enzyme involved in check points

A

Cyclin dependant kinase

If cell is ready, the enzyme phosphorylates a protein

This signals to cell to proceed with cell cycle

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11
Q

Why doesn’t cyclin dependant kinase signal to cell on its own

A

It needs cyclin to activate it

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12
Q

What is quiescence

A

A pause in cell cycle
Without signal such as Anchorage cells dont proliferate

They enter G0 stage (no growth), they can then reenter G1 of apoptosis

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13
Q

What does frequency of cell division depend on

A

How long cell is in G0 or G1 phase

And varies in cell types

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14
Q

How do growth factors signal /stimulate cell growth

A

They will bind to receptor which sends signal for cell to divide

If aren’t present the cell goes to G0

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15
Q

What happens in apoptosis to the cell (programmed cell death)

A

Cell shrinks
Nucleus breaks down
Membrane forms blebs
Organelles in blebs

This then divide and makes several bodies- organelles still function (recycled)

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16
Q

What happens in necrosis (accidental cell death Eg cell is injured)

A

Cell swells
Membrane leaks
Nucleus swells

This means immune cells move to it= causes inflammation

17
Q

Give examples of when apoptosis is triggered

A

If cell is infected- cytotoxic T cells kill it

Embryonic development - remove tissues

If dna is damaged

18
Q

Explain the cycle of how p53 growth factor (tumour suppressor) can cause apoptosis cell death

A

A signal such as dna damage is sent to p53
P53 activation causes mitochondria membrane to rupture

Cytochrome c is released

Activates cascade of caspases(enzymes)

Caspases activate DNAase

Cleaves dna and lamins in nucleus

Causes nuclear fragmentation /cleaved cytoskeleton

Cell detaches from other cells and dies

19
Q

Explain number of chromatids /sister chromatids through each stage of meiosis

A

Start with 92 sister chromatids (46 pairs)

Then division causes 46 sister chromatids (23 pairs)

Divide again into 23 chromosomes when uncondensed

20
Q

What happens in meiosis interphase

A

Maternal chromosomes will replicate into sister chromatids

Paternal will also replicate into sister chromatids

= 46 pairs (23 pairs from each parent)

21
Q

What is the synaptonemal complex

A

Where homologous pairs are drawn together (synapsis) by axial cores (axes) and transverse filaments

22
Q

What is the synaptonemal complex important for

A

Crossing over or homologous pair

23
Q

Explain the 5 stages of prophase

A

Leptonene - sister chromatids condense

Zygotene - the homologous pairs form through the synaptonemal complex

Pachytene- crossing over takes place

Diplotene - synaptonemal complex disappears and chiasma is present

Diakinesis - pair are bivalent ready for metaphase

24
Q

Why are the homologous pairs referred to as tetrad

A

4 chromatids

25
Q

Explain briefly how crossing over takes place

A

A specialised protein breaks both strands on 1 of the chromosomes

This then enables branch migration and forms recombinant homologs

26
Q

What is the spindle equator also called

A

Metaphase plate

27
Q

What is removed in anaphase 1between the pairs

A

Cohesion which kept the pair together removed in disjunction

28
Q

Describe the development of male gametes starting from primary spermatocyte

A

The PS undergoes meiosis 1 and forms 2 secondary spermatocytes

Each SS undergoes meiosis 2 and forms 2 spermatids each

Each spermatid then differentiates into a spermatozoa (spermatogenesis)

29
Q

Explain how a female ovum is developed from a primary oocyte

A

Primary oocyte divides in meiosis 1 into 1 secondary oocyte and the first polar body

In second division the secondary oocyte divides into an ootid and a second polar body

The ootid then develops into an ovum (1 is produced)

30
Q

How is female meiosis different

A

In females meiosis starts at birth and stops after the prophase then at ovulation completed into the secondary oocyte

Only after fertilisation the second division (creating ovum) takes place

31
Q

When do males gametes start to divide my meiosis spermatogenesis

A

After puberty

32
Q

Non disjunction of chromosomes during meiosis produces 2 types of gametes/cells. Name them

A

Aneuploidy - missing chromosomes (monosomic cells)

Trisomy- added chromosomes (trisomic cells )

33
Q

What 2 effects can p53 have on cell division

A

Either stops cell division eg due to dna damage kinases activating p53 to inactivate cyclin dependant kinase

Or by cell apoptosis completely - via caspases and endonucleases

Cell Biology (21 decks)

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