When DNA replication occurs, the DNA strand is being unwound, causing the DNA to be overwound tightly past the replication fork. For example, If you have ever wrapped two strings around each other and then tried to pull part the middle of the string while holding the ends tight, the rest of the string past the place you're pulling the string apart becomes very tight and strained.
Topoisomerase is an enzyme that binds to the DNA and helps release some of that strain by unwinding the DNA past the replication fork.
That means the correct box is the leftmost one. Hope this helps:)
Sexual reproduction happens when there is the involvement of two parents to give rise to the offsprings.
For the production of offsprings, each of the parents produces a haploid gamete and it is by the fusion of these two haploid gametes that a diploid organism is produced.
In the given situation, there are 19 chromosomes present in the haploid gametes this means that a diploid individual will have 2X19 = 38 chromosomes.
Now the underground stem cells are not gametes but somatic cells and the somatic cells are diploid and hence, they will have 38 chromosomes.
