Paper Details | Year: 2012 Session: MAY
Question No: Q5 | Marks: 8.0| Topic: Microbiology| Sub Topic: Cell Cycle
The graph below illustrates how the quantity of DNA, within a mammalian somatic cell,
varies during different phases of the cell’s cycle. Additionally the graph shows the two
growth phases, G1 and G2, which are separated by an intermediate phase S.
0. In terms of the graph above, explain what is happening within the cell during phase S.
During phase S of the cell cycle, the cell is undergoing DNA replication. This is the process in which the cell’s DNA is copied, resulting in the doubling of the amount of DNA present in the cell. This is represented in the graph by the sharp increase in the quantity of DNA during phase S.
1. State ONE process other than cell growth which occurs during phase G2.
During phase G2, the cell is preparing for mitosis. This includes processes such as the condensation of the chromosomes, the formation of the mitotic spindle, and the reorganization of the nuclear envelope. Additionally, the cell may also be involved in processes such as DNA repair and protein synthesis.
2. Account for the changes in the quantity of DNA in the cell during mitosis.
During mitosis, the cell divides into two daughter cells. As a result, the amount of DNA in the cell is halved, as each daughter cell receives an identical copy of the original cell’s DNA. This is represented in the graph by the decrease in the quantity of DNA during mitosis.
3. Explain the significance of mitosis in living organisms.
Mitosis is a vital process in living organisms, as it is responsible for the growth and development of cells. It is also essential for the repair and regeneration of damaged tissues, as well as for the production of new cells. Additionally, mitosis is necessary for the production of gametes, which are required for sexual