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Fundamentals of the living cell > The cell cycle > Flashcards

The cell cycle Flashcards

1
Q

Two things must happen for the cell cycle

A
  1. Duplication of the cell contents e.g. DNA, organelles, cytoplasm…
  2. Division into new progeny cells
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2
Q

How many cycles does it take for unicellular organisms to replicate

A

Each cell cycle gives 2 new organisms

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3
Q

How many cycles does it take for multicellular organisms to replicate

A

Zygote must undergo many rounds of the cell cycle to make a fully grown human

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4
Q

Phases of the cell cycle

A

M, S, G0/G1/G2 phases

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5
Q

Why and which cells are in the G0 phase

A
  1. Cell cycle isnt possible e.g. nerve cells since they are fully differentiated
  2. Maintained in G0 unless stimulated to divide e.g. hepatocytes
  3. Constantly in the cell cycle e.g. epithelial cells of the gut or haematopoietic cells in the bone marrow
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6
Q

How can you visually see the DNA content changing during the cell cycle

A

Fluorescence activated cell sorter (FACS) analysis

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7
Q

Gap 1 phase function

A

Growth and preparation for s phase

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8
Q

S phase function

A

Chromosome duplication

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9
Q

Gap 2 phase function

A

Growth and preparation for M phase

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10
Q

Prophase

A

Chromosomes condense, centrosomes move to opposite poles, mitotic spindles start to form

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11
Q

Prometaphase

A

Nuclear envelope breaks down and chromosomes attach to mitotic spindle

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12
Q

Metaphase

A

Centrosomes are at the opposite poles, chromosomes are at the most condensed state and line up at the equator of the spindle

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13
Q

Anaphase

A

Sister chromatids separate, each new daughter chromatid moving to the opposite pole

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14
Q

Telophase

A

Chromosomes arrive at the spindle poles, chromosomes de-condense and nuclear envelope reforms

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15
Q

Cytokinesis

A

Cytoplasmic division at the position of the metaphase plane. Contractile ring of actin and myosin II constrict the cell into 2 new daughter cells

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16
Q

What makes up the mitotic spindle

A

Bipolar array of microtubules

17
Q

How does the mitotic spindle connect to chromosomes and what is it

A

Via the kinetochore; A large protein structure assembled on the centrosome

18
Q

What are the different types of mitotic spindle

A
  1. Astral
  2. Kinetochore
  3. Interpolar
19
Q

What occurs in meiosis I

A

Homologous chromosomes line up on the spindle fibre and separate to opposite spindle poles

20
Q

What occurs in meiosis II

A

Sister chromatids line up on the spindle and separate to opposite spindle poles

21
Q

What is non-disjunction

A

Failure of homologous chromosomes to separate from one another at either meiotic division I or II

22
Q

what are some non fatal autosome mutations

A

Edwards syndrome - trisomy 18
Patau syndrome - trisomy 13
Downs syndrome - Trisomy 21

23
Q

what are some sex chromosome mutations

A

Turners syndrome - XO
Triple X syndrome - XXX
Klinefelters - XXY

24
Q

summarise the G1 checkpoint

A

Extracellular environment?
Growth factors?
Mitogenic signals?
Check DNA for damage?

25
Q

summarise G2 checkpoint

A

DNA replicated properly?

Check DNA for damage?

26
Q

summarise M checkpoint

A

All chromosomes aligned on the mitotic spindle?

27
Q

what are cyclin dependant-kinases - CDKs

A

Enzymes that phosphorylate target proteins used in the regulation of the cell cycle
Becomes active when bound to a corresponding cyclin

28
Q

What are cyclins

A

Regulators of CDKs, different cyclins are produced at each phase of the cycle

29
Q

What is involved in the cell cycle of yeast

A

S-cyclin binds with CDK to trigger S phase

M-cyclin binds with CDK to trigger M phase

30
Q

Cyclin D pathway

A
  1. Binds to CDK4, activating it
  2. CDK4 partially phosphorylates pRB
  3. E2F is released from pRB
  4. E2F regulated genes can be made allowing the cell to progress from the G1 to S phase
31
Q

How does the cell cycle arrest in the G1 phase so damaged DNA can be repaired

A
  1. P53 will be phosphorylated and activated when the DNA is damaged
  2. P53 will bind to the promoter region of the P21 gene, stimulating its expression
  3. P21 will bind and inhibit G1 CDKs therefore the cell cycle is stopped
32
Q

Cyclin dependant kinase inhibitors

A
  1. INK4 - inhibits cycle progression after G1 point as it inhibits CDK4
  2. CIP/KIP - inhibits all other CDK-cyclin complexes
33
Q

Neoplasia

A

mutated P53 and pRB genes lead to uncontrolled progression through the cell cycle

34
Q

What regulates the early G1 phase

A

Cyclin D and CDK4

35
Q

What triggers the S phase

A

Cyclin E and CDK2

36
Q

What regulates the completion of the S phase

A

Cyclin A and CDK1 and 2

37
Q

What triggers the M phase

A

Cyclin B and CDK1

Fundamentals of the living cell (15 decks)

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