Morgan carried out several dihybrid crosses in Drosophila and found `F_(2)`-rations deviated very significantly from the expected Mendelian ratio. Explain his findings with the help of and example.

Explanation

(i) Morgan hybridised yellow bodied, white eyed female to brown to brown bodied red eyed males. He then intercrossed the `F_(1)` progeny and noticed that the `F_(2)` ratio deviated from the mendel dihybrid ratio of `9 : 3 : 3 : 1`.
(ii) Morgan observed that during his study the proportion of parental gene combinations was much higher than non-parental type. since Morgan knew that his genes of study were located on the X-chromosome, he concluded that physical association or linkage of genes was responsible for this observation.
(iii) Morgan further observed that the formation of non parental types was related to the strength of linkage. The Recombination frequency was much more for genes less tightly linked than got the genes more tightly linked.