The contributions of T.H. Morgan are:

i. Morgan was the first to provide experimental verification for the chromosomal theory of inheritance by his work on Drosophila melanogaster.

ii. He defined linkage between two genes located close together which are always inherited together.

iii. The identified linkage to be of two types tightly linked genes, where both the genes are passed onto the next generation and loosely linked genes in which recombination may take place due to a large distance present within the two genes.

iv. He also defined the term recombination of non – parental gene recombination.

v. His findings of linked genes pavemented the path for genome mapping that is done today.

vi. He also contributed to the understanding of sex – linked inheritance

vii. He has also worked on mutations.