Question

what is a deletion mutation?
○ changing a single purine nucleotide to a pyrimidine nucleotide in a dna molecule
○ the addition of one or more nucleotide pairs to a dna molecule
○ the loss of one or more nucleotide pairs in a dna molecule
○ the replacement of one nucleotide by another nucleotide

Explanation:

A deletion mutation specifically refers to the loss of nucleotide pairs in DNA. Changing a single purine to pyrimidine is a substitution (not deletion). Addition of nucleotide pairs is an insertion mutation. Replacement of one nucleotide by another is substitution. Only the option about loss of nucleotide pairs fits the definition of deletion mutation.

Answer:

the loss of one or more nucleotide pairs in a DNA molecule