How does Rb control the entry of the eukaryotic cell into the S phase?
What will be an ideal response?
Ans: Rb binds the transcription factor E2F and prevents it from activating genes necessary for entry into the S phase. Rb receives signals about DNA damage (from p53) and about cell size. Rb's phosphorylation by the CDK-cyclin complex causes it to release E2F and trigger the entry into the S phase.
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In females, estrogen and progesterone (select all correct choices):
A. direct development of female reproductive structures during embryogenesis. B. direct development of female secondary sexual characteristics during puberty. C. regulate the menstrual cycle and support pregnancy. D. maintain adult health. E. None of these choices are correct.
When an enveloped virus adsorbs to the host cell with its protein spikes, the virions are taken into the cell by the process of
A. penetration. B. production. C. fusion. D. endocytosis.
The cascade of enzyme reactions that ends in clot formation is begun by ________
a. the exposure of collagen in the damaged vessel wall b. albumin contacting the basement membrane c. the conversion of fibrinogen to fibrin d. exposure of blood to air
The structures of prokaryotes that are used to transfer DNA from one cell to another are
A. endospores. B. cilia. C. flagella. D. attachment pili. E. sex pili.