Question

Balance theory of sex determination was proposed by

• A. Waldeyer
• B. T H Morgen
• C. Strassburger
• D. Calvin B Bridges

Answer 1

The correct option is D Calvin B Bridges

The theory of genic balance given by Calvin Bridges (1926) states that instead of XY chromosomes, sex is determined by the genic balance or ratio between X-chromosomes and autosome genomes.
Bridges worked on Drosophila melanogaster. He found that the genic ratio X / of 1.0 produces fertile females whether the flies have XX + 2A or XXX + chromosome complement. A genic ratio X / 0.5 forms a male fruitfully. This occurs in XY + 2A as well as X0 + 2A. It was concluded that the expression of maleness is not controlled by Y- chromosome but is instead localized on autosomes.

So, the correct answer is option D.