CBSE Class 12-science Answered

The genes which determine the traits are carried by the chromosomes from the parents through the gametes to the offspring. This led to the formulation of chromosomal theory of inheritance. This theory was proposed independently by Walter Sutton and Theodore Boveri in 1902. According to this theory:

1. As the sperm and the egg cells serve as a connecting link from one generation to the other, all the hereditary characters must be carried in them.

2. The hereditary factors are present in the nucleus of cells.

3. Like Mendelian alleles, chromosomes are also found in pairs.

4. The sperm and egg having haploid sets of chromosomes fuse to re-establish the diploid state.

5. The genes are carried on the chromosomes.

6. Homologous chromosomes synapse during meiosis and get separated to pass into different cells. This forms the basis of segregation and independent assortment.