Question

7. What is crossing over? Give its significance also. hromntin? Who is it nhseryed clearly?​

Answer 1

Answer:

Crossing over is the process of exchange of genetic material or segments between non-sister chromatids of two homologous chromosomes. Crossing over occurs due to the interchange of sections of homologous chromosomes.

Significance :

1. This process provides an inexhaustible store of genetic variability in sexually reproducing organisms.

2. Useful recombinations are used by the plant and animal breeders. Breeders try to break up the linkages by crossing-over to get combinations of useful traits in the progeny.

3. This process produces a new combination of genes (recombination).

Answer 2

Crossing over is the swapping of genetic material that occurs in the germ line. During the formation of egg and sperm cells, also known as meiosis, paired chromosomes from each parent align so that similar DNA sequences from the paired chromosomes cross over one another.

Significance of crossing over:

(i) Creation of Variability: It leads to the formation of new combinations of genes or the recombination and therefore it is a genetic mechanism to create variability and that is important for improvement of genotypes through the selection.

(ii) Locating Genes: This process is useful for locating genes in the chromosomes.

(iii) Linkage Maps: It plays a vital role in the preparation of linkage maps or chromosome maps which is important as it provides information regarding the frequency of the recombination and sequence of the genes which are further required

(iv) Linear Arrangement of Linked genes: It gives us the evidence for the linear arrangement of linked genes in a chromosome..

(v) Useful for Plant and animal breeders: Useful recombinations are used by the plant and animal breeders. They try to break up the linkage by crossing over in order to get combinations of genes which are recombinants.

Note: Crossing over creates new combinations of genes which you call as recombinants and these genes are formed in the gametes that are not found in either parent, contributing to the genetic diversity. Significance is creation of variability, locating genes, linkage maps etc.