Which of the Following Statements is True

Question

Which of the following statements is true?
A)Sex determination in fruit flies depends on the X : autosome ratio.
B)Mammalian sex determination can be influenced by temperature.
C)Mammals experience random Y inactivation.
D)The testis-determining factor gene is X-linked.
E)Dosage compensation occurs in the same way in most animals.

Accepted Answer

In fruit flies (Drosophila), sex determination is based on the ratio of X chromosomes to autosomes. If the ratio is 1:1, the individual will develop as female, while a ratio of 1:2 results in male development.

B is incorrect because in mammals, sex determination is controlled by genetic factors on the sex chromosomes and is not influenced by temperature.

C is incorrect because in mammals, only one X chromosome in females is randomly inactivated (not the Y chromosome).

D is incorrect because the testis-determining factor (TDF) gene, responsible for male development in humans, is located on the Y chromosome and is not X-linked.

E is incorrect because the process of dosage compensation, which equalizes the expression of X-linked genes in females and males, varies between different animal species. For example, in mammals, dosage compensation is achieved through X inactivation, while in fruit flies, it is achieved through increased transcription of the single X chromosome in males.