Chapter 07 Human Birth Defects

Chapter 07  Human Birth Defects

Complete Chapter Questions And Answers
 

Sample Questions

7. ________ Strong association with late maternal age
A.
47, XXX
B.
45, XO
C.
Trisomy 18
D.
Trisomy 21
E.
47, XXY

ANS: D
Infants with Down syndrome are usually born to older mothers. The mean maternal age is about 35 years compared with 28 in a control population. The older name for this condition is mongolism, coined because of the somewhat slanting look of the eyes. It is an inappropriate name and should not be used.

8. ________ Mental retardation, simian crease, and heart defect
A.
47, XXX
B.
45, XO
C.
Trisomy 18
D.
Trisomy 21
E.
47, XXY

ANS: D
Infants with Down syndrome are mentally retarded (IQ commonly is in the 25 to 50 range) and have heart defects. The single transverse crease (simian crease) in place of the usual curved crease is found in about 50% of people with the syndrome. It is also found in people with other chromosomal abnormalities and in about 1% of normal people. The presence of a simian crease does not necessarily indicate a chromosomal abnormality and Down syndrome, but it is a useful criterion when associated with other characteristics (mental retardation hypotonia, epicanthal folds, furrowed and protruding tongue).

9. ________ Sterile male with chromatin-positive nuclei
A.
47, XXX
B.
45, XO
C.
Trisomy 18
D.
Trisomy 21
E.
47, XXY

ANS: E
Males with chromatin-positive nuclei have Klinefelter syndrome or a related condition. Newborn males appear normal, but the testes remain abnormally small as puberty approaches owing to hyalinization of the seminiferous tubules. Consequently, they are sterile. Secondary sexual characteristics develop poorly, and gynecomastia (enlargement of breasts) may occur. These men typically are tall and eunuchoid and may have a subnormal mentality.

10. ________ Antitumor agent and potent teratogen
A.
Cytomegalovirus
B.
Androgenic agents
C.
Thalidomide
D.
Toxoplasma gondii
E.
Aminopterin

ANS: E
Aminopterin, an antitumor agent, is also a potent human teratogen. Methotrexate, a derivative of aminopterin, is also teratogenic. These agents produce a wide range of severe skeletal defects and anomalies of the central nervous system (CNS). Aminopterin may produce meroanencephaly (anencephaly), intrauterine growth retardation, and many other CNS abnormalities.