Question

During primary sex determination in mammals, the presence of Sry gene on the Y-chromosome is the major factor in determining if male or female gonads will develop. Expression of Sry protein activates the Sox9 gene, which triggers the expression of testis-forming genes and blocks the expression of ovary-forming genes. XY females are genotypically male but phenotypically female. If 15% of XY females have the Sry gene, why do they phenotypically develop into females?

a
Normal Sry protein is produced, which transcriptionally activates the Sox9 gene.

b
Although normal Sry protein is expressed, the gonads are able to express higher levels of the ovary-forming genes

c
There are mutations in the Sry gene so that it encodes for a non-functional protein

d
The Sry gene is not expressed in XY females

Answer 1

a. Normal Sry protein is produced, which transcriptionally activates the Sox9 gene.