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.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A), (C) and (D) only
Thomas Hunt Morgan worked with the fruit fly Drosophila and gave the experimental proof of the chromosomal theory of inheritance.
(A) His experiment led to discovering the basis for the variation that sexual reproduction produced. — Correct. His work on linked genes showed that recombination of genes on chromosomes produces the variation seen after sexual reproduction.
(B) He mapped the position of genes on the chromosomes. — Incorrect. Gene mapping was done by Alfred Sturtevant, Morgan’s student. He used the frequency of recombination between gene pairs as a measure of the distance between them.
(C) He coined the term linkage. — Correct. Morgan used linkage for the physical association of genes on a chromosome, and recombination for non-parental combinations.
(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. — Correct. The two genes did not segregate independently, and the F2 ratio was far from Mendel’s 9 : 3 : 3 : 1.
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