Which of the following types of mutation, resulting in an error in the mRNA just after the AUG start of translation, is likely to have the most serious effect on the polypeptide product?
A) a deletion of a codon
B) a deletion of two nucleotides
C) a substitution of the third nucleotide in an ACC codon
D) a substitution of the first nucleotide of a GGG codon
E) an insertion of a codon

B

What is the effect of a nonsense mutation in a gene?
A) It changes an amino acid in the encoded protein.
B) It has no effect on the amino acid sequence of the encoded protein.
C) It introduces a premature stop codon into the mRNA.
D) It alters the reading frame of the mRNA.
E) It prevents introns from being excised.

C

A frameshift mutation could result from
A) a base insertion only.
B) a base deletion only.
C) a base substitution only.
D) deletion of three consecutive bases.
E) either an insertion or a deletion of a base.

E

Which of the following DNA mutations is the most likely to be damaging to the protein it specifies?
A) a base-pair deletion
B) a codon substitution
C) a substitution in the last base of a codon
D) a codon deletion
E) a point mutation

A

Which small-scale mutation would be most likely to have a catastrophic effect on the functioning of a protein?
A) a base substitution
B) a base deletion near the start of a gene
C) a base deletion near the end of the coding sequence, but not in the terminator codon
D) deletion of three bases near the start of the coding sequence, but not in the initiator codon
E) a base insertion near the end of the coding sequence, but not in the terminator codon

B

The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. This results in
A) a base-pair substitution.
B) a nucleotide mismatch.
C) a frameshift mutation.
D) a polypeptide missing an amino acid.
E) a nonsense mutation.

D

A mutation results in a defective enzyme A. Which of the following would be a consequence of that mutation?
A) an accumulation of A and no production of B and C
B) an accumulation of A and B and no production of C
C) an accumulation of B and no production of A and C
D) an accumulation of B and C and no production of A
E) an accumulation of C and no production of A and B

A

Which of the following mutations would be most likely to have a harmful effect on an organism?
A) a nucleotide-pair substitution
B) a deletion of three nucleotides near the middle of a gene
C) a single nucleotide deletion in the middle of an intron
D) a single nucleotide deletion near the end of the coding sequence
E) a single nucleotide insertion downstream of, and close to, the start of the coding sequence

E