Advanced Placement (AP) Biology Practice Exam

What is a characteristic of individuals with Turner Syndrome regarding their X chromosomes?

1. One X chromosome is duplicated

2. Both X chromosomes are present

3. Part of one X chromosome is deleted

4. An extra Y chromosome is present

The correct answer is: Part of one X chromosome is deleted

Individuals with Turner Syndrome typically have a characteristic that involves the presence of only one X chromosome, which can lead to various developmental and health-related issues. In many cases, part of one X chromosome could be deleted, which results in the associated symptoms of Turner Syndrome. The condition is a result of a complete or partial absence of one of the X chromosomes, which is often denoted as 45,X or variants like 46,X,i(Xq), where "i(Xq)" represents an isochromosome of the long arm of the X chromosome. Understanding the genetic makeup in Turner Syndrome is crucial, as the missing or altered genetic information can lead to features such as short stature, ovarian insuficiency, and various heart defects, among others. This deletive aspect on the X chromosome directly relates to the condition's manifestation, helping to clarify why recognizing the deletion is significant when discussing the genetic characteristics of Turner Syndrome.