Question

Answer each question with an explanation. (Cell Biology)

1)Mitogens such as EGF ______.
a. cause cells to proceed through M phase
b. Induce inactivation of Ras
c. inhibit Rb

2)The G1 checkpoint ________.
a. causes cells to proceed through S phase more quickly
b. involves the stabilization of p53
c. is activated by errors caused during DNA replication

3)The contractile ring divides the cell in two. Three main proteins are involved. Which of the following proteins does not localize to the contractile ring?
a. Actin
b. Myosin
c. Microtubule
d. Intermediate filament

4)Which of the following statements is false?
a. Activated M-Cdk induces condensation of DNA into chromosome
b. Activated S-Cdk induces cell cycle arrest
c. G₁-Cdk inactivates Retinoblastoma protein

5)Bcl2 is _____.
a. Pro-apoptotic protein
b. Anti-apoptotic protein

Answer 1

1) Mitogens such as EGF is responsible for a. causing cells to proceed through M phase. Epidermal growth factor causes progression from the G2 phase to M phase.

2) The G1 checkpoint c. is activated by the errors which are caused during DNA replication. Defects during DNA replication or DNA damage due to any other reason cause the activation of G1 checkpoint. ATM/ATR pathway is activated and phosphorylated by DNA damage and it further activates checkpoint kinases.

3) d. Intermediate filament does not localize to contractile ring. Contractile ring is assembled in anaphase and activated when the cells divide.

4) b. Activated S-Cdk induces cell cycle arresting is a false statement. Activation of S-Cdk causes further growth and division of the cells.

5) Bcl2 is an b. anti-apoptotic protein. Bcl2 prevents apoptosis by prevention the release of antiapoptogenic factors from mitochondria.