Define crossing over. What is the significance of crossing over ?

Explanation

Crossing over. The mutual exchange of segments between nonsister chromatids of two homologous chromosomes to produce new combinations of genes is called cross over. Importance of Crossing Over. 1. It brings new combination of genes which are different from parents. This introduces variations. The variations are helpful in struggle for existence and adaptability to changes in environment. 2. Variations form a platform for natural selection to act. 3. Useful recombinations are picked up by breeders for development of improved varieties. 4. It contributes towards evolution. 5. It is established that genes occur in a linear fashion over the chromsomes. 6. The frequency of crossing over is used for building linkage maps or chromosome maps. 7. The rarity or abundance of a particular combination of genes is known from frequency of crossing over 8. The phenomenon has helped in understanding the effect of different genes over themselves as well as over the organism.