Answer
Oftentimes, unmethylated cytosine will lose its amino group to form uracil as the result of a mutagen. This error is usually detected and repaired by the cell, since uracil is identified to not belong in DNA. However, when 5′−methylcytosine loses its amino group, the product is thymine, which is accepted as a correct nucleotide and is therefore neglected by the DNA repair mechanism. During replication, the mismatch repair mechanism recognizes the mismatched pair, automatically matching a new C to the G or a new A to the T, resulting in a mutation.
Work Step by Step
Oftentimes, unmethylated cytosine will lose its amino group to form uracil as the result of a mutagen. This error is usually detected and repaired by the cell, since uracil is identified to not belong in DNA. However, when 5′−methylcytosine loses its amino group, the product is thymine, which is accepted as a correct nucleotide and is therefore neglected by the DNA repair mechanism. During replication, the mismatch repair mechanism recognizes the mismatched pair, automatically matching a new C to the G or a new A to the T, resulting in a mutation.
