Question

What are the conclusions drawn by T.H. Morgan from the crossing experiment in Drosophila with respect to linkage?

Answer 1

Hint: T.H. Morgan performs experiment on Drosophila to observe sex-linked traits. He observed that not all the genes are segregating in F2 generation. He also explained the concept of distance of genes and linkage. This experiment is called chromosomal theory of inheritance.

Complete answer:
Thomas Hunt Morgan is a American zoologist and geneticist. He is famous for his experimental research with the fruit fly (Drosophila melanogaster). By this experiment he explained the chromosomal theory of inheritance. He did this experiment to show how sexual reproduction gave rise to variations.
Morgan conducts an experiment between yellow bodied, white-eyed females and brown-bodied, red-eyed males. The F2 generation does not satisfy the Mendel’s Dihybrid ratio. He observed that segregation does not occur between two genes as per Mendel law. He explained that if two genes are present on the same chromosome than higher parental combinations are observed in offspring. This type of physical association is called linkage.
He also concluded that the probability of recombination is dependent on how strong the linkage is. Some genes show high linkage and less recombination while some of them show weak linkage. The frequency of linked genes also gives the possibility of appearance of particular traits in the next generation.
He concluded that closer the genes, greater the linkage and vice-versa.

Note: He also discovered the white eye mutation in Drosophila. He chooses Droshophila to study the sex-linked genes. The mutation is inherited differently by male and female flies he said. He also concluded that the X chromosome consists of the eye color gene. Recombination of genes is also explained by this.