31. A genetic defect in humans results in the absence of sweat glands in the skin. Some men have this defect all over their bodies, but in women it is usually expressed in a peculiar way. A woman with this defect typically has small patches of skin with sweat glands and other patches where sweat glands are lacking. This pattern suggests the phenotypic effect of
(a) a mutation
(b) chromosome inactivation
(c) RNA splicing
(d) an operon
32. Which of the following is correct with regard to aneuploidy?
(a) inversion
(b) 2n + 1
(c) All aneuploid individuals die before birth
(d) 4n
33. If a fragment of a chromosome breaks off and then reattaches to the original chromosome but in the reverse direction, the resulting chromosomal abnormality is called
(a) a deletion (b) an inversion
(c) a translocation (d) a nondisjunction
34. Why are individuals with an extra chromosome 21, which causes Down syndrome, more numerous than individuals with an extra chromosome 3 or chromosome 16?
(a) There are probably more genes on chromosome 21 than on the others
(b) Chromosome 21 is a sex chromosome and 3 and 16 are not
(c) Down syndrome is not more common, just more serious
(d) Extra copies of the other chromosomes are probably fatal
35. Humans have 23 pairs of chromosomes, while our closest relatives, chimpanzees, have 24. Chromosome studies indicate that at some point early in human evolution, two chromosomes simultaneously broke into a large portion and a small portion. The large parts combined to form a large chromosome, and the small parts combined to form a much smaller chromosome (which was subsequently lost). This important chromosomal change could best be described as
(a) nondisjunction followed by deletion
(b) translocation followed by deletion
(c) duplication followed by deletion
(d) translocation followed by inversion
36. Each cell in an individual with Down syndrome contains ____ chromosomes.
(a) 47 (b) 22
(c) 24 (d) 45
37. Disorders involving unusual numbers of sex chromosomes show that maleness is caused by the
(a) presence of an X chromosome
(b) presence of a Y chromosome
(c) absence of an X chromosome
(d) absence of a Y chromosome
38. A particular allele can have different effects if it was inherited from a male rather than a female. This phenomenon is known as
(a) extranuclear inheritance
(b) genome imprinting
(c) sex-linkage
(d) Prader-Willi syndrome
39. Human mitochondria
(a) are inherited as an X-linked trait
(b) are all inherited from the father
(c) have linear DNA
(d) are all inherited from the mother
40. Both chloroplasts and mitochondria
(a) are found within the nucleus
(b) have linear DNA
(c) carry extranuclear genes
(d) display a Mendelian pattern of inheritance
