A geneticist searching for mutations uses the restriction endonucleases SmaI and PvuII to search for mutations that eliminate restriction sites. SmaI will not cleave DNA with CpG methylation. It cleaves DNA at the restriction digestion sequence ↓ 5′−CCC GGG−3′ 3′−GGG CCC−3′ ↑ PvuII is not sensitive to CpG methylation. It cleaves DNA at the restriction sequence ↓ 5′−CAG CTG−3′ 3′−GTC GAC−5′ ↑ What common feature do SmaI and PvuII share that would be useful to a researcher searching for mutations that disrupt restriction digestion?

Key Concepts

Restriction Endonucleases

Restriction endonucleases, or restriction enzymes, are proteins that cut DNA at specific sequences, known as restriction sites. Each enzyme recognizes a unique sequence of nucleotides and cleaves the DNA at or near this site. Understanding how these enzymes function is crucial for geneticists, as they can be used to analyze DNA fragments and identify mutations that may disrupt these specific sequences.

Methylation and Its Effects

DNA methylation is a biochemical process involving the addition of a methyl group to the DNA molecule, often affecting gene expression and the ability of restriction enzymes to cleave DNA. For instance, SmaI is inhibited by CpG methylation, meaning it cannot cut DNA at its recognition site if that site is methylated. Recognizing how methylation influences enzyme activity is essential for understanding how mutations can affect restriction digestion.

Common Features of Restriction Enzymes

Despite their differences in sensitivity to methylation, SmaI and PvuII share the common feature of recognizing specific palindromic DNA sequences for cleavage. This characteristic allows researchers to utilize these enzymes to identify mutations that disrupt these sequences, as any alteration could prevent the enzyme from binding and cutting the DNA. Understanding this shared feature is vital for geneticists searching for mutations that affect restriction digestion.