What is linkage ? Give two factors affecting linkage.

Explanation

Linkage is the phenomenon of certain genes staying together during inheritance through generations without any change or separation due to their being present on the same chromosome. Linkage was first suggested by Sutton and Boveri in 1902. It was Morgan (1910) who clearly proved and defined linkage on the basis of his breeding experiments in fruitfly Drosophila melanogaster. Morgan.s famous chromosomal theory of linkage states that (i) Linked genes occur in the same chromosome. (ii) They lie in a linear sequence in the chromosome. (iii) There is a tendency to maintain the parental combination of genes except for occasional crossovers. Factors affecting linkage. 1. Distance. Strength of the linkage between two genes is inversely proportional to the distance between the two, i.e., two linked genes show higher frequency of crossing over if the distance between them is higher and lower frequency if the distance is small. 2. Age of Organism. With increasing age, the chances of crossing over are reduced and hence strength of linkage increases.