Imagine discovering a loss-of-function mutation in a eukaryotic gene. You determine the gene's nucleotide sequence from the start site for transcription to the termination point of transcription and find no differences from the wild-type sequence. Explain where you think the mutation might be and how the mutation might be acting.

If a base-pair change occurs in DNA, this a. is a mutation. b. would be a mutation only if it falls in a protein-coding part of a gene. c. would be a mutation only if it falls in a transcribed part of the genome. d. is not a mutation, because only one base pair has been altered.

A geneticist found that a particular mutation had no effect on the polypeptide encoded by a gene. This mutation probably involved

a. Deletion of one nucleotide

b. Alteration of the start codon

c. Insertion of one nucleotide

d. Substitution of one nucleotide

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 non-disjunction

Which of the following mutations would be most likely to have a harmful effect on an organism?

a. A deletion of three nucleotides near the middle of a gene

b. A single nucleotide deletion in the middle of an intron

c. A single nucleotide deletion near the end of the coding sequence

d. A single nucleotide insertion downstream of, and close to, the start of the coding sequence

Which of the following describes mutations? Select True or False for each statement.

T/F Point mutations can occur in any DNA sequence.

T/F Frameshift mutations can occur in any DNA sequence.

T/F Neutral mutations depend on the degeneracy of the genetic code.

T/F Deleterious mutations occur only in protein-coding sequences of DNA.