Write the scientific name of the organism Thomas Hunt Morgan and his colleagues worked with for their experiments. Explain the correlation between linkage and recombination with respect to genes as studied by them. How did Sturtevant explain gene mapping while working with Morgan?

a) Thomas Hunt Morgan and his colleagues worked with Drosophila melanogaster, commonly known as the fruit fly. Explanation: Dihybrid cross was carried out on these fruit flies. Yellow bodied, white-eyed females were crossed with brown bodied, red-eyed males. The results observed after F2 generation was different than that of Mendel's dihybrid cross. The reason for deviation was the location of the gene involved on the chromosome. Two very closed genes will have very few recombination events and be tightly linked, while two genes that are slightly apart will have more recombination events and be less tightly linked.
b) Alfred Sturtevant utilised the knowledge of the frequency of gene combination as a measure of physical distance between two genes and to map their positions on the chromosomes.