Which common model organism is known for the white-eyed mutation and studied by Thomas Hunt Morgan?

Which common model organism is known for the white-eyed mutation and studied by Thomas Hunt Morgan?

• A. Mice
• B. Zebrafish
• C. Yeast
• D. Fruit fly

Answer: (D)

Think of how inheritance patterns reveal where genes reside. The fruit fly, Drosophila melanogaster, is a classic model organism because it reproduces quickly and its visible traits are easy to track. Thomas Hunt Morgan studied a white-eyed mutation in this species and used it to show that genes are carried on chromosomes, not floating independently. The white-eyed trait is recessive and located on the X chromosome, so males with just one X can express it if they inherit the X with the white allele, while females need two copies to show it. Morgan’s crosses produced patterns that lined up with X-linked inheritance: the trait appeared in males more often and followed a sex-linked pattern across generations. This work helped establish the chromosome theory of inheritance and solidified the fruit fly’s role as a key genetic model.

Think of how inheritance patterns reveal where genes reside. The fruit fly, Drosophila melanogaster, is a classic model organism because it reproduces quickly and its visible traits are easy to track. Thomas Hunt Morgan studied a white-eyed mutation in this species and used it to show that genes are carried on chromosomes, not floating independently. The white-eyed trait is recessive and located on the X chromosome, so males with just one X can express it if they inherit the X with the white allele, while females need two copies to show it. Morgan’s crosses produced patterns that lined up with X-linked inheritance: the trait appeared in males more often and followed a sex-linked pattern across generations. This work helped establish the chromosome theory of inheritance and solidified the fruit fly’s role as a key genetic model.