The term linkage was coined by -

The correct answer is Option (4) → T. H. Morgan

Linkage is the physical association of genes on the same chromosome. Linked genes stay together in inheritance, so they do not assort independently.

(1) Henking — Incorrect. In 1891 he traced a special nuclear structure through sperm formation in insects and named it the X body. This was the first step towards sex chromosomes.

(2) Sutton and Boveri — Incorrect. They showed that chromosomes behave like Mendel’s genes. They did not coin the term linkage.

(3) Gregor Mendel — Incorrect. He gave the laws of inheritance. The genes he studied in peas sorted independently.

(4) T. H. Morgan — Correct. In Drosophila dihybrid crosses, genes on the same chromosome gave parental combinations far more often than new ones. Morgan explained this by the physical association of the genes and coined the term linkage. He also coined the term recombination for the new combinations.

NCERT Extract:
Linkage and Recombination – …

Figure 4.11 Linkage: Results of two dihybrid crosses conducted by Morgan. Cross A shows crossing between gene y and w; Cross B shows crossing between genes w and m. Here dominant wild type alleles are represented with (+) sign in superscript