Question

The term linkage was coined by

Answer 1

The concept of linkage was firstly reported by Bateson and Punnett but T.H. Morgan by experimenting with fruit fly coined the term linkage and put forth the theory of linkage and gave the conclusions about the cis and trans phenomenon of the linkage.
Mendel for the first time performed his experiments on garden pea plants (Pisum sativum) for eight years with 14 varieties to understand the pattern of inheritance and variation in living organisms. Experiments resulted in the groundbreaking discovery of principles of inheritance. The traits that Mendel studied were present on different chromosomes, assort independently and were not linked. The tendency of genes on the same chromosomes to remain in their original combination during inheritance is ensured by the linkage. Mendel was unaware of the concept of linkage, he performed a hybridization experiment on pea plants and concluded the laws of inheritance on the basis of the assortment, segregation and dominance of the factors.
Morgan crossed normal fruit fly with red eyes and white eye fruit fly and produced $F_1$, and intercrossed between the heterozygous $F_1$ red eyed flies, traits in the $F_2$ progeny did not assort independently, he was expecting the frequency in 1:1:1:1. In the yielded result he got a result deviating from his expectations. As per his expectation he was supposed to get 50% red and 50% white in both the sexes but it didnot appear as such. There were no white eyed females, Morgan wondered and crossed again between original white eyed male and one $F_1$ female, then the white eyed female did appear in the progeny. Morgan then hypothesized that they eye colour is connected with the sex factor, this in turn gave rise to the idea of genetic linkage.