DNA replication is a process in which the synthesis of the new strand takes place from parental DNA or strand.
DNA polymerase is an important enzyme that is responsible for the adding of the nucleotide and thus forms a new strand.
During the process of synthesis one strand is synthesized in continuous forms that goes toward the replication fork and called as a leading strand that moves in 3' to 5' direction.
The other strand that is synthesized in pieces form that is known as lagging strand and the pieces of the DNA is joined by an important enzyme known as DNA ligase.
According to the question, mating between two populations of Rhagoletis produce hybrid flies.
This means that the two population is present in the same habitat or locality, hence they are capable of coming in contact with each other and mate. Hence, the answer cannot be Habitat Isolation.
Mating produces hybrid flies. This is possible when the gametes (egg and sperm) of the two different populations are capable of capable of coming close to each other and undergoing fusion (fertilization). Hence, there is no Mechanical Isolation.
The zygote formed by the above fertilization is capable of developing into healthy hybrid flies with normal life span. Hence, Pre-zygotic Isolation is absent.
But the hybrid flies formed are sterile and not fertile, that is, they are incapable of producing viable gametes which can undergo fertilization and produce a new offspring.Therefore, the eggs laid by the hybrid flies hatch less often. Hence, there is existence of Reduced hybrid fertility.
