Question

QUESTION 1

1. Which of these proteins is responsible for preventing cell cycle progression if DNA damage is detected?

   		Rb
   		p53
   		ras
   		E7

1 points   

QUESTION 2

1. Which of the following is a proto-oncogene?

   		Cyclin
   		Cdk
   		ras
   		All of the above

1 points   

QUESTION 3

1. The photograph below shows a chromosome. In what phase of the cell cycle was the cell from which this chromosome taken?


   $xid-25303092_1$

   		G1
   		S
   		G2
   		M
   		Interphase

1 points   

QUESTION 4

1. Which of the following microtubule behaviors can be observed in cells during anaphase?

   		(+)-end polymerization
   		(+)-end depolymerization
   		Both (+)-end polymerization and depolymerization
   		Neither (+)-end polymerization nor depolymerization

1 points   

QUESTION 5

1. What is the “point of no return” for proliferation and therefore the most important checkpoint in the Eukaryotic cell cycle?

   		G1/S
   		S/G2
   		G2/M
   		G0
   		The spindle assembly checkpoint

Answer 1

1. p53 is the protein that causes growth arrest, DNA repair and apoptosis. Its levels are low in the normal cell. However, in DNA damaged cells, p53 levels rise to induce DNA repair, arrest cell cycle and induce apoptosis of DNA damaged cells. E7 protein causes disassembly of E2F1 transcription factor from pRB protein, thereby inactivating it. E7 protein therefore causes increased cell division. RB protein prevents excessive cell division by blocking entry of cells into S phase. Ras protein is a proto-oncogene, then which is converted to oncogene, which will increase cell division.

Right choice: p53

2. Cyclins and CDK (cyclin dependent kinases) complexes are involved in each stage of normal cell cycle. It is Ras, which is a proto-oncogene. It is converted to oncogene when there is DNA damage. As a result, there is increased cell division.

Right choice: Ras.

3. As the image is not seen/visible, this question cannot be answer.

5. The G1 to S transition is the point of no return. There is a gap between the end of mitosis and when the next DN replication initiates. It is at the G1/S transition that the cells commit for DNA replication. Once, the cell has entered S phase, DNA replication will occur and the cells will have to undergo cell division.

Right choice: G1/S.

As HOMEWORKLIB’s rules, there is necessity to answer only one question.