Question

For a cell that is right after DNA replication, where 2n=6

a. Is this cell haploid, diploid, or tetraploid?

b. How many molecules of DNA are there?

c. Are chromosomes single stranded or double stranded?

d. How many chromosomes are there

e. How many homologous pairs are there

f. How many unique chromosomes are there

g. How many sister chromatid pairs are there

Thank you very much!

Answer 1

It given that the cell has 2n = 6, means it is a diploid cell where n= 3. replication is a process in which the DNA molecule is copied to produce identical daughter molecule with high fidelity.

a- DNA molecules are replicated but the number of chromosomes that are in nucleus determines the ploidy remains unchanged after S phase or replication phase. So ploidy is same before and after S phase i,e diploid.

b. After the S phase or replication, the amount of DNA per cell doubles but the chromosome number doesn't changes.

c.After replication the chromosomes become double stranded and the two chromatids get attached to a single centromere

d. The chromosomes number is 6 only. As the DNA molecules get replicated and get arranged in a single centromere so the number of chromosomes don't change, it will remain 6 only.

e. There will be 6 homologus pair of chromosomes in the cell after repliacation, each having a pair of chromatids.

f. After the replication process all DNA molecules get copied & number of chromosomes remain same, it means all the chromosomes are double stranded bound to a single centromere. So, no unique chromosomes are there in the cell after repliacation.

g. As 2n=6 so there are 6 chrmosomes and when all get replicated then the sister chromatids became 12 in number. When we talk about sister chromatid pairs it will be equal to 6 pairs.