Question

Describe the genetic balance theory of sex determination.

Answer 1

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. In Drosophila, Y chromosome is not involved in the process of sex determination. The value of the ratio X/A is considered for the fly to be female or male. A single X chromosome in a diploid individual will make it male. The pair of X chromosomes in a diploid individual make it female. In the other mammals, the Y chromosome plays an important role in determining the male sex. The presence of XX chromosome states that the individual is female and the presence of XY states that the individual is male.