Which of the following is not the karyotype of turners syndrome?
**Core Concept**
Turner syndrome is a genetic disorder that affects females, characterized by the partial or complete absence of one X chromosome. The typical karyotype of Turner syndrome is 45,X, indicating the absence of one X chromosome.
**Why the Correct Answer is Right**
The correct karyotype for Turner syndrome is 45,X, resulting from a non-disjunction event during meiosis, where one X chromosome fails to separate from the other. This leads to the presence of only one X chromosome in the cells of affected individuals. The other options do not accurately represent the karyotype of Turner syndrome.
**Why Each Wrong Option is Incorrect**
**Option A:** 46,XX is the typical karyotype for a female with two X chromosomes, not indicative of Turner syndrome.
**Option B:** 47,XX,+21 represents the karyotype for Down syndrome, not Turner syndrome.
**Option C:** 46,XY is the typical karyotype for a male, who by definition has one X and one Y chromosome.
**Clinical Pearl / High-Yield Fact**
It's essential to recognize the characteristic karyotype of Turner syndrome, 45,X, for accurate diagnosis and management.
**Correct Answer: A. 46,XX**