Briefly mention the contribution of T.H. Morgan in genetics.
T.H. Morgan experimentally verified the chromosomal theory of inheritance through his work with Drosophila melanogaster (fruit flies). He carried out several dihybrid crosses to study sex-linked genes and observed that when two genes were located on the same chromosome, they did not segregate independently, and the F₂ ratio deviated significantly from the expected 9:3:3:1 ratio.
Morgan coined the term linkage to describe the physical association of genes on a chromosome. He also coined the term recombination to describe the generation of non-parental gene combinations. Additionally, he discovered that genes could be tightly linked (showing very low recombination) or loosely linked (showing higher recombination).
Explanation
The context highlights Morgan's key contributions: (1) experimental verification of chromosomal theory of inheritance using Drosophila, (2) discovery that genes on same chromosome don't segregate independently, (3) coining the terms 'linkage' and 'recombination', and (4) finding that genes can be tightly or loosely linked. These points are sufficient for a 2-mark answer as they cover his major contributions to genetics.
Solution Steps
Step 1: Identify Morgan's role in verifying chromosomal theory of inheritance
Step 2: Mention his work with Drosophila and dihybrid crosses
Step 3: Highlight his discovery of linkage and recombination concepts
Step 4: Include his findings about tight and loose linkage