Chapter 15

Question 1

One day a 9-year-old girl surprisingly
announces to her mother, “Guess what,
mommy, I’m not a girl; I’m a boy.” The mother
is shocked but does not act on the comment.
During the next few years, the mother notices
some tomboyish behavior and difficulty in
social adjustment at school. When the girl is 12
years old, puberty starts with a striking virilization
of the external genitalia. The mother is
extremely concerned and seeks medical attention.
What is the most likely cause?
(A) Male pseudointersexuality
(B) Female pseudointersexuality
(C) Congenital adrenal hyperplasia
(D) Testicular feminization
(E) Illegal use of anabolic steroids

Answer 1

A. Reduced levels of androgens during fetal development of a XY male fetus cause feminization
of the male external genitalia such that the baby can be phenotypically mistaken for female. Parents raise the XY male baby as a girl until puberty or other medical problems bring the child
to medical attention.

Question 2

The most common cause of female
pseudointersexuality is
(A) a 46,X0 genotype
(B) a 47,XXY genotype
(C) lack of androgen receptors
(D) congenital adrenal hyperplasia
(E) inadequate production of testosterone
and miillerian-inhibiting factor (MIF)

Answer 2

D. Female pseudointersex individuals have a 46,XX genotype. This condition is most commonly
caused by congenital adrenal hyperplasia, in which the fetus produces excessive amounts
of androgens. The high androgen level masculinizes the female genitalia.

Question 3

The most common cause of male pseudointersexuality
is
(A) a 45,X0 genotype
(B) a 47,XXY genotype
(C) inadequate production of testosterone
and MIF
(D) congenital adrenal hyperplasia
(E) lack of androgen receptors

Answer 3

C. Male pseudointersex individuals have a 46,XY genotype. This condition is most commonly
caused by inadequate production of testosterone and MIF by the fetal testes. The low testosterone
and MIF levels stunt the development of the male genitalia.

Question 4

The Y chromosome carries a gene on its
short arm that codes for
(A) testosterone
(B) MIF
(C) testes-determining factor (TDF)
(D) progesterone
(E) estrogen

Answer 4

C. The gene product that is coded on the short arm of the Y chromosome is called the testesdetermining
factor (TDF).