Question

Short / Long answer type questions
How do variations arise in sexually reproducing organisms? Explain very briefly.

Answer 1

• In sexually reproducing organisms, during prophase-I of meiosis the homologous pairs of chromosomes come together (synapsis) and exchange of segments of chromosomal segments occur between the two homologous chromosomes. The crossing over and exchange of the chromosomal segments occurs between non-sister chromatids. This, therefore, helps in the exchange of genetic materials from the two parents and introduce a new chromosome complement leading to new traits in the offspring. So, crossing over results in variations in sexually reproducing organisms.
  
• 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.