Question

1. A human cell has a total of 23 chromosome pairs at the beginning of interphase. How many total DNA molecules would exist during prophase of that dividing cell?

2. A human cell has a total of 23 chromosome pairs at the beginning of interphase. How many total chromosomes would exist during prophase of that dividing structure?

3. A human cell has a total of 23 chromosome pairs at the beginning of interphase. How many total DNA strands would exist during prophase of that dividing structure?

Answer 1

1) before mitosis DNA replicates so each chromosome has 2 DNA molecules attached to each other at the centromere, so during prophase number of DNA molecules=number of chromosomes $\times$ 2=46$\times$2=92

(number of chromosomes =2$\times$23=46)

2) even the DNA is replicated during S phase the DNA molecules are attached to each other at the centromere so number of chromosomes does not change

number of chromosomes in the prophase=number of chromosomes =2$\times$23=46

3) each DNA is double-stranded

so number of DNA strands= 2$\times$number of DNA molecules=2$\times$92=184