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1

1. The eukaryotic cell cycle is composed of four phases in the following order:
a. G1; S; G2; M
b. G1; G2; S; M
c. G1; M; G2; S
d. S; G1; G2; M

a. G1; S; G2; M

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2. The length of time it takes for the cells labeled during DNA synthesis to begin to enter mitosis is a good estimate of the length of the _______ phase(s).
a. G1
b. S
c. G2
d. M

c. G2

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3. In a typical cycling mammalian cell, _______ of the cell cycle is spent in interphase.
a. 99%
b. 95%
c. 75%
d. 50%

b. 95%

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4. Cell cycles of early embryonic animal cells are unusual because they have
a. no G1 or G2.
b. an elongated G1 and G2.
c. a short S.
d. a much shortened M.

a. no G1 or G2., c. a short S.

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5. The number of cells in the different phases of a population can be determined most easily by using a(n) _______ to measure the amount of DNA per cell in a large sample of cells.
a. scintillation counter
b. flow cytometer
c. fluorescence microscope
d. phase-contrast microscope after autoradiography

b. flow cytometer

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6. Cells in the quiescent phase of the cell cycle are said to be in the _______ phase.
a. G0
b. G1
c. G2
d. M

a. G0

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7. Which of the following represents the amount of DNA in a typical G2 cell?
a. n
b. 2n
c. 4n
d. 8n

c. 4n

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8. The G1 checkpoint in budding yeast cells is called
a. START.
b. the restriction point.
c. the decision point.
d. the G1/S boundary.

a. START.

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9. The G1 checkpoint in animal cells is called
a. START.
b. the restriction point.
c. the decision point.
d. the G1/S boundary.

b. the restriction point.

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10. Skin fibroblasts arrested in G0 are stimulated near a wound to enter G1 by _______ growth factor.
a. epidermal
b. fibroblast
c. platelet-derived
d. keratinocyte

c. platelet-derived

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11. The G2 checkpoint prevents entry into _______ if _______.
a. G1; DNA synthesis is not complete and/or DNA is damaged
b. S; DNA synthesis is not complete and/or DNA is damaged
c. G2; DNA synthesis is not complete and/or DNA is damaged
d. M; DNA synthesis is not complete and/or DNA is damaged

d. M; DNA synthesis is not complete and/or DNA is damaged

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12. Maturation promotion factor (MPF), discovered by Masui and Markert, is the factor that
a. is missing in the cdc2 mutant in yeast.
b. induces entry into meiosis when injected into frog oocytes.
c. fluctuates in amount during early cleavages of sea urchin eggs.
d. fluctuates in amount during the cell cycle of mammalian cells.

b. induces entry into meiosis when injected into frog oocytes.

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13. MPF is a
a. monomeric protein kinase.
b. dimer of two molecules of Cdk1.
c. dimer of Cdk1 and cyclin A.
d. dimer of Cdk1 and cyclin B.

d. dimer of Cdk1 and cyclin B.

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14. MPF is a general regulator of the transition from
a. G1 to S.
b. S to G2.
c. G2 to M.
d. metaphase to anaphase.

c. G2 to M.

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15. Studies on cell cycle mutants in budding and fission yeasts demonstrated that cdc2 and cdc28 both encode a
a. protein kinase.
b. protein phosphatase.
c. ubiquinating enzyme.
d. growth factor.

a. protein kinase.

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17. To become active, Cdk1 must
a. bind cyclin.
b. bind cyclin and be phosphorylated on tyrosine 15 and threonines 14 and 161.
c. bind cyclin and be phosphorylated on tyrosine 15, and be dephosphorylated on threonines 14 and 161.
d. bind cyclin and be phosphorylated on threonine 161, and be dephosphorylated on threonine 14 and tyrosine 15.

d. bind cyclin and be phosphorylated on threonine 161, and be dephosphorylated on threonine 14 and tyrosine 15.

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19. Which cyclin(s) is/are required to pass the G1 restriction point in animal cells?
a. Cyclin A
b. Cyclin A and Cyclin B
c. Cyclin D
d. Cyclin D and Cyclin E


d. Cyclin D and Cyclin E

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20. Passage of animal cells through the cell cycle is regulated primarily by
a. the availability of nutrients.
b. intracellular second messengers.
c. extracellular growth factors.
d. direct cell surface interactions.

c. extracellular growth factors.

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21. The retinoblastoma protein (Rb) binds to and inhibits
a. transcription factor E2F.
b. oncogenes.
c. cyclin-dependent kinase.
d. p53.

a. transcription factor E2F.

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22. Growth-factor stimulation of the Ras/Raf/ERK pathway initially stimulates the synthesis of cyclin
a. A.
b. B.
c. C.
d. D.

d. D.

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24. Damaged DNA is sensed by a complex of proteins that activate the protein kinase
a. ATM or ATR.
b. ABS.
c. Akt.
d. MCM.

a. ATM or ATR.

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25. The disease ataxia telangiectasia, which causes nervous system defects and a high frequency of cancer in affected individuals, results from a mutation in the gene for the protein
a. ATM.
b. ABS.
c. Akt.
d. MCM.

a. ATM.

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26. To prevent cells with unreplicated DNA from passing through the G2 checkpoint, Chk1 and Chk2 _______ and _______ protein phosphatase Cdc25.
a. phosphorylate; stimulate
b. phosphorylate; inhibit
c. dephosphorylate; stimulate
d. dephosphorylate; induce the degradation of

b. phosphorylate; inhibit

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27. p21 inhibits cell cycle progression by binding to and inhibiting
a. cyclin-dependent kinases.
b. p53.
c. ATM.
d. Rb protein.

a. cyclin-dependent kinases.

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28. Nuclear envelope breakdown occurs at the _______ of _______.
a. beginning; prophase
b. end; prophase
c. end; prometaphase
d. beginning; anaphase

b. end; prophase

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30. During prophase, Cdk1/Cyclin B (MPF) directly phosphorylates all of the following except
a. condensins.
b. lamins.
c. APC/C.
d. microtubule-associated proteins.

c. APC/C.

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32. Chromosomes are attached to spindle microtubules by
a. centromeres.
b. kinetochores.
c. centrioles.
d. centrosomes.

b. kinetochores.

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33. Polar microtubules
a. overlap in the center of the spindle.
b. are attached to the contractile ring.
c. are attached to kinetochores.
d. pull kinetochores poleward.

a. overlap in the center of the spindle.