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Genetics > Cell Cycle > Flashcards

Cell Cycle Flashcards

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1
Q

What does mitosis result in

A

2 genetically identical diploid daughter cells

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2
Q

What does meiosis I result in? Meiosis II?

A

Meiosis I - two genetically different haploid cells

Meiosis II - 4 haploid cells - two identical pairs

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3
Q

What does crossing over occur?

A

Prophase I

Re-assortment of genetic material between homologous or paired chromosomes

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4
Q

What are the phases of cell cycle

A

G1 - gap after mitosis of cell from previous cycle and before DNA synethsis

S - DNA synthesis

G2 - gap between completion of DNA synthesis and start of cell division

M - mitosis - cell division

(G0) - non dividing cells such as corneal endothelium, neurones remain in resting noncycling state

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5
Q

What controls progression through cell cycle?

A

Cyclins

Cyclin dependent kinases stimulate cell cycle progression by phosphoylating specific proteins in the cell required for transiion to the next stage

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6
Q

What is the restriction point in G1

A

Once passed the cell is committed to completing its cell division

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7
Q

What occurs at the G1-S checkpoint?

A

Ensures that previous cycle of division has been completed and any resultant damage repaired

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8
Q

What gene acts at the G1-S checkpoint

A

p53 gene - tumour suppressor gene - restricts entry of cells with damaged DNA to the S phase - regulates passage of cell through the restriction point

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9
Q

What happens at the G2-M chekpoint

A

Ensures that dNA synthesis and resultant damage are repaired before mitosis occurs

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10
Q

What arethe phases of mitosis

A

Prophase
Prometaphase
Metaphase
Anaphase
Telophase
Cytokinesis

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11
Q

What happens in prophase?

A

Cells chromatin condenses
Chromosomes become visible as a pair of sister chromatids - joined at centromere

Centrioles duplicate and migrate towards opposite poles of cell

Spindle of microtubules is formed - nucleoli disperse

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12
Q

Prometaphase in mitosis

A

Breakdown of nuclear envelope
Formation of kinetochores - attachment point between chromosomes and the spindle at the centromere

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13
Q

Metaphase (mitosis)

A

Chromosomes attach to the spindle by the kinetochore and line up to form equatorial plate

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14
Q

Anaphase (mitosis)

A

Centromeres separate and the chromatids and pulled to opposite poles by spindle

Clustering of complete set of chromosomes at each pole of the cell

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15
Q

Telophase (mitosis)

A

Chromosomes begin to uncoil again
Nuclear membrane reforms
Nucleoli reappear

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16
Q

Cytokinesis (mitosis)

A

Cleavage forms in middle of cell dividing in two

17
Q

Prophase 1 (meisois)

A

Homologous chromosomes come together and cross over, exchange segments in homologous recombination

18
Q

Process of prophase 1 (meiosis)

A

Leptopene - spindle forms

Zygotene - chromosomes shorten, thicken

Pachytene - chiasmata form - crossing over

Diplotene - exchange of genetic material between homologous chromosomes

Diakinesis - recombinant chromosome formed

19
Q

Metaphase 1 (meiosis)

A

Chromosomes attach to the spindle

20
Q

Anaphase 1 (meiosis)

A

Whole chromosomes migrate to opposite poles)

21
Q

Telophase 1 (meiosis)

A

2 genetically different haploid cells are formed

22
Q

What happens in meiosis 2

A

In anaphase II - sister chromatids separate rater than chormosomes - forming 2 identical pairs of haploid cells (4 cells altogether)

23
Q

What processes generate genetic diversity?

A

Chiasmata formation from corssoing over in prophase I - random exhage of genetic material between homologous chromosomes

Independent segregation of homologous chromosomes occurs during anaphase I

24
Q

How many combinations possible in gamaets

A

2^23 combinations

25
Q

What is formed in meiosis of oocytes?

A

One definitive oocyte
One secondary oocyte
One polar body

26
Q

What is apoptosis?

A

Cell death that is programmed

After intra or extracellular physiological triggers during development/remodelling, defence, homeostasis, ageing

Pyknosis - condensation of nucleus
Karyorrhexis - nucles fragments)
Cells shrink
Organelles maintain structure
Cell membrane forms irregular buds
Cells break into smaller bodes
Phagocytosed by macrophages

27
Q

What is pyknosis?

A

Condensation and fragmentation of chromatin
Condenses into patches against the nuclear envelope as a result of endonuclease activity

28
Q

What is karyorrhexis?

A

Nuclear envelope becomes discontinuous and DNA fragments

29
Q

What induces p53? What does it do

A

Tumour suppressor gene

Induced by DNA damage
TRanscription factor results in arrest of cell cycle in G1 to allow DNA repair

30
Q

What does Hcl-2 do

A

Suppresses some apoptotic pathways
rEduction in levels of Bcl-2 associated with apoptosis

31
Q

What are telomeres?

A

Repetitive DNA sequences found at the end of chromosomes
Synthesised by telomerase - no replicated in the same way as other chromosomal DNA

32
Q

How is apoptosis initiated?

A

Direct result of TNF production by macrophage

Fas ligand binds Fas receptor - formation of death inducing signalling complex (DISC) - contains FAS assocatied protein with Death Domain (FADD), caspase-8 and caspase-10
Sequence of events triggers apoptosis

Genetics (7 decks)

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