[Campbell Biology P.406] Small-scale mutations within a gene are divided into two general ca... | Practice Question

Small-scale mutations within a gene are divided into two general categories. What are these categories, and which type is exemplified by the cause of sickle-cell disease?

  • A: Deletions and insertions; sickle-cell disease is caused by a deletion.
  • B: Substitutions and translocations; sickle-cell disease is caused by a translocation.
  • C: Substitutions and nucleotide-pair insertions/deletions; sickle-cell disease is caused by a nucleotide-pair substitution.
  • D: Frameshift mutations and point mutations; sickle-cell disease is caused by a frameshift mutation.

Explanation

The text states that 'Small-scale mutations within a gene can be divided into two general categories: 1 single nucleotide-pair substitutions and 2 nucleotide-pair insertions or deletions.' It further clarifies that sickle-cell disease is caused by 'a mutation of a single nucleotide pair in the gene that encodes hemoglobin,' which is a classic example of a nucleotide-pair substitution, specifically changing a C to an A on the template strand CTC to CAC . Therefore, the correct categories are substitutions and nucleotide-pair insertions/deletions, with sickle-cell disease being a substitution.