Question

How is the no: of chromosomes and the amount of DNA is maintained in the individual during sexual reproduction

Answer 1

The sexual mode of reproduction incorporates the process of combining DNA from two different individuals. How is the problem of doubling of chromosomes overcome?
OR 
How is specific chromosome number maintained in a sexually reproducing organism?
OR
How are the number of chromosomes and the DNA content reestablished when germ cells (sex cells) from two individuals combine during sexual reproduction to form a new individual?

The reproductive organs of sexually reproducing organisms produce gametes (sex cells) by a special type of cell division. In this cell division the chromosome number is halved. That is, the diploid mother cell produces haploid sex cells (gametes) containing only half the number of chromosomes. During fertiuisation, when the haploid male and female gametes Rise, they form a diploid zygote. Thus, the full number of chromosomes is reestablished and the specific chromosome number of a species is maintalned.

Answer 2

the number of chromosomes is maintained in the individual during sexual reproduction as the gene cells use certain mechanism which results in reduction of the total number of chromosomes to half the amount present in other cells.