Question

In metamale Drosophila, chromosome combination is

• A. 3X: 2A
• B. 3X: 3A
• C. XY: 3A
• D. XY: 2A

Answer 1

Answer: (C)

XY: 3A

Genic Balance Theory was proposed by C.B. Bridges in 1922 for sex determination in Drosophila. It states that ratio of number of X-chromosome to that of the complete set of autosome determines the sex of Drosophila. According to this theory of sex determination, if the ratio of X chromosome to a total number of sets of autosomes (X/A) is >1, the organism will be super female. If the ratio of X chromosome to a total number of sets of autosomes (X/A) falls between 1 and 0.50, the genotype will show the intersex phenotype. The X/A value is 1.0 for normal female and 0.5 for the normal male. If the ratio of X chromosome to a total number of sets of autosomes (X/A) is below 0.50, the organism will be metamale. In the given question, the ratio of X/A is 1/3 that is XY: 3A.

Thus, the correct answer is option C.