The karyotype in testicular feminising syndrome is?

**Core Concept**
Testicular feminizing syndrome, also known as androgen insensitivity syndrome, is a rare genetic disorder affecting sex development. It occurs due to mutations in the androgen receptor gene (AR), leading to a deficiency in androgen receptor function. This condition results in a male individual with predominantly female external genitalia.

**Why the Correct Answer is Right**
In testicular feminizing syndrome, the individual has a 46,XY karyotype, which is characteristic of males. This is because the condition is caused by mutations in the androgen receptor gene, which is located on the X chromosome, and not by a chromosomal abnormality. The presence of testes and the production of androgens are normal, but the body is unable to respond to these hormones due to the defective androgen receptor. This leads to the development of female external genitalia and secondary sexual characteristics.

**Why Each Wrong Option is Incorrect**
**Option A:** This choice is incorrect because testicular feminizing syndrome is not associated with a 46,XX karyotype, which is typical of females.
**Option B:** This choice is incorrect because testicular feminizing syndrome is not associated with a 47,XXY karyotype, which is characteristic of Klinefelter syndrome.
**Option C:** This choice is incorrect because testicular feminizing syndrome is not associated with a 45,X karyotype, which is characteristic of Turner syndrome.

**Clinical Pearl / High-Yield Fact**
Testicular feminizing syndrome is a rare cause of primary amenorrhea in females, but it can also present in individuals who appear male at birth but develop female secondary sexual characteristics during puberty.

**Correct Answer:** C. 46,XY.