**Question:** Males who are sexually underdeveloped with rudimentary testes and prostate glands, sparse pubic and facial hair, long arms and legs, and large hands and feet are likely to have the chromosome complement of:

A. XY
B. XXY
C. XO
D. 47, XXXY

**Correct Answer:** D. 47, XXXY

**Core Concept:**
The clinical presentation described in the question refers to Klinefelter syndrome, a genetic condition caused by the presence of an extra X chromosome in males. This results in a karyotype of 47, XXXY. Individuals with Klinefelter syndrome often exhibit underdeveloped secondary sexual characteristics, such as rudimentary testes, prostate glands, and sparse body hair. They may also have long limbs, large hands and feet, and a tall stature.

**Why the Correct Answer is Right:**
Klinefelter syndrome is caused by the presence of an extra X chromosome (47, XXXY) in males. The extra X chromosome leads to decreased production of testosterone due to the inactivation of one of the X chromosomes. Testosterone is essential for the development of male secondary sexual characteristics, such as testes, prostate, pubic, and facial hair.

**Why Each Wrong Option is Incorrect:**
A. XY: This is the normal chromosome complement for males (46, XY). The presence of an extra X chromosome distinguishes Klinefelter syndrome from this normal condition.

B. XXY: This represents Klinefelter syndrome, so it is not the correct answer. The extra X chromosome causes the underdeveloped secondary sexual characteristics seen in the question.

C. XO: This refers to Turner syndrome, a condition characterized by the absence of one X chromosome (45, XO). Klinefelter syndrome has an extra X chromosome (47, XXXY), which leads to the clinical features described in the question.

D. 47, XXXY: This is the correct answer as it represents the karyotype of individuals with Klinefelter syndrome. The extra X chromosome leads to the clinical features described in the question.

**Clinical Pearl:**
Klinefelter syndrome is a relatively common genetic condition, affecting approximately 1 in 500-600 males. The condition can lead to infertility, short stature, and developmental delays, in addition to the clinical features described in the question. Early identification and supportive care, including speech therapy, occupational therapy, and psychological support, can significantly improve the quality of life for individuals affected by Klinefelter syndrome.