Mutation

Which of the following is correct with regard to aneuploidy?

• (a) inversion

• (b) 2n + 1

• (c) All aneuploid individuals die before birth

• (d) 4n

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

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

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

Each cell in an individual with Down syndrome contains ____ chromosomes.

• (a) 47

• (b) 22

• (c) 24

• (d) 45

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

Which of the following is a change in the sequence that leads to formation of a stop codon?

• missense mutation

• nonsense mutation

• silent mutation

• deletion mutation

The formation of pyrimidine dimers results from which of the following?

• spontaneous errors by DNA polymerase

• exposure to gamma radiation

• exposure to ultraviolet radiation

• exposure to intercalating agents

Which of the following is an example of a frameshift mutation?

• deletion of a codon

• missense mutation

• silent mutation

• deletion of one nucleotide

A wild-type chromosome can be represented as ABC*DEFGH, and from this a chromosomal aberration arises that can be represented as ABC*DEGFH. This is known as a: (* = centromere)

• a) Deletion

• b) Duplication

• c) Translocation

• d) paracentric inversion

• e) pericentric inversion