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TLS Online TPP Program

#Question id: 12482

The Rb protein has been called the “master brake” of the cell cycle. How the Rb protein acts as a cell cycle brake?

#Unit 2. Cellular Organization
  1. Rb bound to E2F and function as transcriptional repressors because Rb recruits chromatin-modifying enzymes that promote deacetylation and methylation of specific histone lysines, causing chromatin to assume a condensed, transcriptionally inactive form.
  2. S phase CDKs and mitotic CDKs maintain Rb protein in the phosphorylated state throughout the S, G2, and early M phases.
  3. Rb bound to E2F and promotes ubiquitinylation of E2F and inhibits chromosomal segregation.
  4. Rb bound to E2F and promotes acetylation which prevents unloading of cohesins.
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TLS Online TPP Program

#Question id: 12184

#Unit 2. Cellular Organization

Following graph represent Control of S phase onset in S. cerevisiae by regulated proteolysis of the S phase inhibitor Sic1. 
Which of the following is correct according to graph?
TLS Online TPP Program

#Question id: 12183

#Unit 2. Cellular Organization

Following statements are regarding to regulation of S phase and mitotic cyclin levels in budding yeast.
A. In late anaphase, the anaphase-promoting complex (APC/C) ubiquitinylates S phase and mitotic cyclins.
B. In late anaphase, the anaphase-promoting complex (APC/C) phosphorylates S phase and mitotic cyclins.
C. During exit from mitosis and G1, Cdh1 is dephosphorylated and active; during S phase and mitosis, Cdh1 is phosphorylated and dissociates from APC/C, and APC/C becomes inactive.
D. During exit from mitosis and G1, Cdh1 is phosphorylated and active; during S phase and mitosis, Cdh1 is dephosphorylated and dissociates from APC/C, and APC/C becomes inactive.
E. The G1/S phase CDKs, which themselves are not APC/CCdh1 substrates, phosphorylate Cdh1 at the G1–S phase transition.
F. The G1/S phase CDKs, which themselves are not APC/CCdh1 substrates, ubiquitinylates Cdh1 at the G1–S phase transition.
Which of the following combination is correct?
TLS Online TPP Program

#Question id: 12182

#Unit 2. Cellular Organization

The cell cycle is controlled by protein kinases that comprise a catalytic subunit and a regulatory subunit. Which of the following statement is correct regarding to these subunits?
TLS Online TPP Program

#Question id: 4718

#Unit 2. Cellular Organization

All the following statements about destruction of cyclins are true, except:
TLS Online TPP Program

#Question id: 2994

#Unit 2. Cellular Organization

If a cell has completed meiosis I and the first cytokinesis, and is just beginning meiosis II, which of the following is an appropriate description of its genetic contents?
TLS Online TPP Program

#Question id: 2993

#Unit 2. Cellular Organization

During meiosis, a defect occurs in a cell that results in the failure of spindle microtubules binding at the kinetochores. Which of the following statements describes the most likely result of such a defect?