Question

In Drosophila, the formation of gynandromorph and their cytological explanation provide the best evidence that
A. X chromosome plays an important role in sex determination.
B. X chromosome does not play any role in sex determination.
C. Y chromosome does not play any role in sex determination.
D. Y chromosome is required for maleness.

Answer 1

Drosophila is also known as fruit fly. It is known to study the principles of fundamental genetics. In Drosophila, sex determination is achieved by the balance of female determinants on the X-chromosome and male determinants on autosomes.

Complete answer: Sex determination is a system that helps in determining the development of sexual characteristics in an organism. The offsprings are obtained when two opposite sex’s organism reproduce sexually. In sexually reproducing organisms, male and female fuse to form a zygote. The gametes have haploid chromosomes. There are two types of chromosomes; autosomes, which determine the phenotype and sex chromosomes, which are associated with sexual characteristics.
The Drosophila has both X and Y chromosomes including autosomes. The cell decides whether the organism will be male or female irrespective of the organism. It results in the formation of gynandromorphs. Gynandromorphs are individuals who contain both male (XO) and female (XX) characteristics. The male character is present in one part and the female character in another. In Drosophila, it results due to the loss of one X chromosome during the first mitotic division. Thus, Y chromosomes are not responsible for the determination of sex. In butterflies and birds, males are homozygous (ZZ) and the females are heterozygous (ZW).
Thus, the correct answer is option C.

Note: The Y chromosome in Drosophila encodes genes that are necessary for producing sperms. In humans, the presence or absence of the Y chromosome decides the sex. In females, XX chromosome is present, whereas, in males XY is present.