Which of the following statements are correct with respect to T.H. Morgan?

(A) His experiment led to discovering the basis for the variation that sexual reproduction produced.
(B) He mapped the position of genes on the chromosomes.
(C) He coined the term linkage.
(D) He crossed yellow-bodied, white-eyed Drosophila females to brown-bodied red-eyed Drosophila males and observed the results contrary to that of Mendel's.

Choose the correct answer from the options given below.

(A), (C) and (D) only

The correct answer is Option (4) → (A), (C) and (D) only    

Experimental verification of the chromosomal theory of inheritance by Thomas Hunt Morgan and his colleagues, led to discovering the basis for the variation that sexual reproduction produced.

Boveri and Sutton's chromosome theory of inheritance stated that genes are found at specific locations on chromosomes, and that the behavior of chromosomes during meiosis can explain Mendel’s laws of inheritance.

Morgan introduced the term "linkage" after conducting dihybrid cross experiments involving the fruit fly Drosophila. During these crosses, he noted that two genes did not always assort independently as described by Mendel's laws. His observations revealed that when two genes are located on the same chromosome, the occurrence of the parental combination is notably higher in the subsequent generation compared to the non-parental combination.

Morgan carried out several dihybrid crosses in Drosophila to study genes that were sex-linked. The crosses were similar to the dihybrid crosses carried out by Mendel in peas. For example Morgan hybridised yellow-bodied, white-eyed females to brown-bodied, red-eyed males and intercrossed their F1 progeny.  During these crosses, he noted that two genes did not always assort independently as described by Mendel's laws. His observations revealed that when two genes are located on the same chromosome, the occurrence of the parental combination is notably higher in the subsequent generation compared to the non-parental combination. He observed that the two genes did not segregate independently of each other and the F2 ratio deviated very significantly from the 9:3:3:1 ratio (expected when the two genes are independent).