Question

You have studies mitosis in onion root tip cell it has 14 chromosome in each cell . can you tell how many chromosome will the cell have G1 phase after S phase and after M phase ? Also what will be the DNA content of the cell at G1 after Sphase and G2 phase . if the contain after Mphase is 2c

Answer 1

G1 phase is the 1st Gap phase in the cell cycle. in this there is no change in both Chromosome numer and DNA content.

As S phase is the Synthesis phase all the DNA will get duplicated to form its own sister chromatids. But Chromosome number will remain same becuase number of chromosome will be same as number of centromere.

M phase is the division phase where cell division occurs. in this all the chromosome will condense to form a proper structure with 2 chromatids and one centromere. here the chromosome will allighn in an imaginary metaphase plate. and the chromosome number and DNA content will be the same as S phase.

After M phase CHromosome number will be same but the content will be the half of of M phase because of the cleavage in centromere.

And chromosome number of onion is 16 not 14.

G1 phase -

Chromosome NO : 16

DNA content : 1 N

S phase

Chromosome NO : 16

DNA content : 2 N

M phase

Chromosome NO : 16

DNA content : 2 N

After M phase

Chromosome NO : 16

DNA content : 1 N