Question

Short / Long answer type questions
The progeny of a sexually reproducing organism is never the replica of the parents in all respects. Mention any four factors that cause this variation.

Answer 1

The reasons for the appearance of variation among the progeny formed by sexual reproduction is mentioned below:-

1. The genetic material is exchanged between chromosomes before forming of the zygote. Deoxyribonucleic acid (DNA) exchange in the chromosome. This results in forming of variation in the progeny.
   
2. Crossing over causes the DNA to be exchanged between the homologous chromosomes during meiosis. It occurs during gamete production, as a result, gamete produced by an individual does not have the same genetic material as of the individual. This crossing over adds the variation during the transfer of genetic material from parent to offspring. So, the offspring will not have the same set of chromosomes but have a recombined form from parents.
3. The separation of sister chromatids and their random distribution to daughter cells or gametes is one another reason for the generation of variations in sexually reproducing organisms.
4. During sexual reproduction, the DNA copying mechanism is not accurate, and the resultant errors are a source of variations in populations of organisms.