Question

Write a short note on crossing over.

Answer 1

Crossing over is the mutual exchange of blocks of homologous genes between a pair of homologous chromosomes during meiosis. It occurs during prophase I when non-sister chromatids of homologous chromosomes break and rejoin, resulting in new combinations of genes. This process increases genetic variation by producing recombinant chromosomes and is significant for genetic mapping and evolution. Factors like gene distance, age, X-rays, and temperature affect crossing over frequency.