Question

In Drosophila the XXY condition leads to femaleness whereas in human beings the same condition leads to Klinefelter’s syndrome in male. It proves that
A) In human beings, Y chromosome is active in sex determination.
B) Y chromosome is active in sex determination in both human beings and Drosophila.
C) In Drosophila Y chromosome decides femaleness.
D) Y chromosome of man has genes for syndrome

Answer 1

Hint: Drosophila melanogaster is a species of fly in the family Drosophilidae. The species is known generally as the common fruit fly or vinegar fly.

Complete Answer:
- Klinefelter syndrome is a genetic condition that occurs due to trisomy of sex chromosome (XXY) that means a boy is born with an extra copy of X chromosome. They develop secondary sex character of female like large breast and loss of facial hair.
- Such children are born as a result of fertilization of abnormal eggs (XX) by normal sperms with X or Y chromosome or by fertilization of normal eggs with (X) chromosomes by abnormal sperms with (XY) chromosome.
- In Drosophila, sex determination is achieved by a balance of female determinants on the X chromosome and male determinants on the autosomes.
- While in case of human beings two sex chromosome in male XY and females XX. Every individual must have at least one X chromosome.
- Therefore the presence of one extra X chromosome in male leads to a genetic disease while in Drosophila only X chromosomes are present and hence an increase in numbers of X chromosomes leads to femaleness only.

In Drosophila presence or absence of Y chromosome does not affects the sex of the organism but in human Y chromosome decide the male gender.

Note: That’s why the XXY condition leads to femaleness in Drosophila but in human beings the same condition leads to Klinefelter’s syndrome in male. Therefore option A is the correct answer.