What is crossing over? Give its significance.

Crossing over is a process that occurs during meiosis, specifically during prophase I, where homologous chromosomes exchange segments of their genetic material. This exchange happens between non-sister chromatids of homologous chromosomes, resulting in a recombination of genetic information.

The significance of crossing over includes:

1. Genetic Variation: It increases genetic diversity by creating new combinations of alleles in the offspring. This genetic variation is crucial for evolution and adaptation in populations.
2. Chromosome Pairing: It helps in the proper alignment and segregation of homologous chromosomes during meiosis, ensuring accurate distribution of chromosomes to the gametes.
3. Gene Mapping: By analyzing the frequency and patterns of crossing over, scientists can map the relative positions of genes on chromosomes. This is useful for understanding genetic linkage and for locating genes associated with specific traits or diseases.

Overall, crossing over is a fundamental process that contributes to genetic diversity and the proper functioning of meiosis.