Question
Biology Question on Principles of Inheritance and Variation
In Drosophila, the sex is determined by
The ratio of number of X-chromosome to the sets of autosomes
X and Y chromosomes
The ratio of pairs of X-chromosomes to the set of autosomes
Whether the egg is fertilized or develops parthenogenetically
The ratio of number of X-chromosome to the sets of autosomes
Solution
According to genic balance theory of sex determination the ratio between the number of X-chromosomes and number of complete sets of autosomes will determine the sex. The X-chromosome is believed to carry female tendency genes, while autosomes carry male tendency genes. Both these sets of genes start functioning and there has to be a balance between them for an individual to become male or female. If the ratio between X and A is 1.0 it will be a female individual and when it is 0.5, it would be male.