Write differences between linkage and crossing over.

Feature Linkage Crossing over Definition The linkage is the association of genes or any DNA sequences on the same chromosome. Crossing over is the exchange of genetic material during sexual reproduction between non-sister chromatids of two homologous chromosomes that form recombinants. Feature Linkage Crossing over Relation of the distance The strength of the genetic linkage between two genes is inversely proportional to the distance between them in the chromosome. The probability of two genes crossing over is directly proportional to the distance between them in a chromosome.

Define chromosomal theory of inheritance.

Chromosomal theory of inheritance was proposed by Sutton and Boveri (1904). It states that: The gametes have all the hereditary characters. These are the genetic link between two generations. The genetic material is present within the nucleus in the form of chromosomes and the chromosomes occur in pairs. During gamete formation, the homologous chromosome pair segregate independently by a process called meiosis. Thus, each gamete contains only one set of chromosomes. The fusion of sperm and ovum happens during fertilization due to which the diploid number of chromosomes is retained.