Question

In which phase of the cell cycle are sister chromatids available as templates for repair?
A. G1 phase
B. G2 Phase
C. S phase
D. M phase

Answer 1

Hint: By homologous recombination a DNA strand can be repaired . On a homologous chromosome, Sister chromatids are present. The phase in which the chromatids are available as a template in that phase sister chromatids are repaired through the process of homologous recombination.

Complete Answer:
To solve this question we must know about the phases of cell division.
1. G1 phase- (Growth1) It is an intermediate phase between the end of M phase and beginning of S Phase. During the G1 phase the cell prepares for DNA replication and also duplication of the centrosome takes place.
2. G2 phase- it is the period in which a cell undergoes protein synthesis and cell growth. The cell prepares itself for mitosis. This phase acts as a checkpoint for the cell before entering the mitotic phase. The cell repairs the damaged chromatids or proteins. If the repair does not take place, the cell division is arrested at this phase.
3. S phase- Synthetic phase is very important as duplication of genome takes place during this phase.
4. M-phase- It is the phase of cell division where the cell splits into two daughter cells.

Hence the answer is B) G2 phase.

Note: In particular, due to the high replication activity and the formation of single-ended replication fork-associated breaks in S phase and the critical G2 phase preceding the subsequent division in M phase, error-free repair of Double Stranded Bases in S/G2 is important.