Question

Onion root tip cells have 14 chromosomes in each cell. Can you tell how many chromosomes will the cell have at G1 phase, after S phase, and after M phase? Also, what will be the DNA content of the cells at G1, after S, and at G2 if the content after M phase is 2C?

Answer 1

Hint:- Cell cycle contains the order of events that occur to prepare the cell for cell division. It consists of G1, S, G2, and M phases. The G1, G2, and S phases are part of the interphase.

Complete step-by-step solution:-G1 phase marks the initiation of the DNA replication. In this phase, chromatin fibers become slender, less coiled, and active for transcription. So in this phase, the number of chromosomes will remain the same i.e 14.
During the S phase the amount of DNA doubles. DNA replication takes place. Replication takes place in semiconservative nature. As there is no doubling of chromosome so now also the amount of chromosome would remain the same in the cell which is 14.
During the M phase, the cells divide to form two daughter cells. The division is equally distributed. So the amount of chromosomes gets distributed equally in the daughter cells. The daughter cells will have 14 chromosomes each.
If the DNA content after the M phase is 2C then it would remain the same in the G1 phase. As the S phase leads to replication of DNA so the amount of DNA in the cell will be 4C and it would remain the same in the G2 phase also.

Note:-
The cell cycle is mainly composed of two phases - interphase and then M phase. In interphase, the cell is prepared for division, and replication of genetic material takes place in the cell. The cell remains active during the whole phase. When it enters the M phase the cells divide itself and distribute the content equally in the daughter cells.