Sample Questions and Answer From Past Exams

Answer the following questions in 10 - 20 words:

1.   What biochemical event initiates differentiation of early gonads into testes around the seventh week?

Minimum complete answer:
TDF

More elaborate answer:
Cells in the indifferent gonads begin to express the SRY gene and thereby produce testis development factor (TDF), also called H-Y androgen.  This single event initiates sex differentiation of the male embryo.

Common wrong answer(s):
Testosterone or other androgens do not initiate differentiation.  These are produced after the gonads have already differentiated into testes.

2.   What causes female pseudohermaphroditism?

Minimum complete answer:
Androgen exposure in utero

More elaborate answer:
Female pseudohermaphrodites possess a normal complement of female sex chromosomes (XX) and develop normal ovaries.  However, exposure to excessive androgens in utero leads to virilization of the external genitalia, particularly clitoral enlargement and labial fusion.  The most common cause of this condition is congenital adrenal hyperplasia.  Two other minor causes are the administration of adrogenic agents to the mother and androgen-producing maternal tumors.

Common wrong answer(s):

• Female pseudohermaphrodites are not genetic males (XY).
• This condition does not involve disjunction of the sex chromosomes.  XXY is Klinefelter's Syndrome.

Minimum complete answer:
Hole in the interatrial septum to shunt oxygenated blood from right to left atria.

More elaborate answer:
The foramen ovale is an anatomic adaptation in the fetus to allow oxygenated blood coming from the umbilical vein via the inferior vena cava to bypass the pulmonary circulation.  Due to higher pressure on the right side of the heart, blood is shunted from the right atrium through a hole in the interatrial septum to the left atrium, from where it continues into the left ventricle and hence to the systemic circulation.  Functional closure of the foramen ovale normally occurs at birth.

Common wrong answer(s):

• The foramen ovale is not something to do with the ovaries or the uterus.
• The foramen ovale is not an artery or vein, not does it connect any other of the many anatomic structures that people guessed.

Minimum complete answer:
Conduit between the umbilical vein and the inferior vena cava that shunts oxygenated blood past the liver.

Elaborate answer:
The ductus venosus is a fetal anatomic adaptation that allows roughly half the oxygenated blood coming from the umbilical vein to bypass the liver microcirculation and continue straight to the heart via the IVC.  The ductus venosus degenerates after birth.

Common wrong answer(s):

• The ductus venosus  is not something to do with the ovaries or the uterus.
• The ductus venosus does not connect any other of the many anatomic structures that people guessed.

Define plasticity in the context of growth and development, and give two situations in which the tissues of an adult’s body might demonstrate plasticity?

The best answers defined plasticity as the ability of cells and tissues to alter their structure and function in response to genetic and environmental cues, especially during critical periods.

The biggest problem was that many students included disease processes in their definition of plasticity.  The body may attempt to compensate or adapt in specific ways to maintain adequate structure and function in response to disease, but the damage caused by diseases or defects does not in and of itself illustrate plasticity.  Plasticity is the sculptor continually reshaping her sculpture to please her changing aesthetics.  Disease is someone else attempting  to take a sledgehammer to it.