Question

‘Genic balance theory’ was forwarded by,
(A) Lillie
(B) Crew
(C) Lederberg and Tatum
(D) C B Bridges

Answer 1

Hint: Genic balance theory was proposed by an American scientist. He was born in New York in 1889. He lost both his mother and father at an early age. His grandmother used to take care of him.

Complete answer:
Genic balance theory was forwarded by C B Bridges in 1921. He made his study on Drosophila. The genic balance theory also explains why there are sexual variants in fruit fly such as meta-males, intersex, and meta-females other than normal males and females.

According to C B Bridges, the sex in drosophila is determined by the ratio of the number of X chromosomes to that of the number of sets of autosomes.
If the ratio of $\frac { X }{ A } $ is 1.00, then the individual will be female.
If the ratio of $\frac { X }{ A } $ is 0.50, then the individual will be male.
If the ratio of $\frac { X }{ A } $ is between 1.00 and 0.50, the individual will be intersex.
If the ratio of $\frac { X }{ A } $ is above 1.00, the individual will be metafemale.
If the ratio of $\frac { X }{ A } $ is below 0.50, the individual will be meta males.
So, the correct answer is ‘C B Bridges’.

Note: Meta females are the females who are mostly sterile. They are also known as super females. These females are often taller than the average. Similarly, meta males are mostly sterile.
An intersex is usually a person who is born with reproductive anatomy which neither fits into male nor into the female.