Practice question

Restriction endonucleases recognize specific palindromic tetra- to octanucleotide sequences and introduce double-strand breaks at those sites. A single nucleotide polymorphism within recognition motif abolishes existing site or creates new site, altering fragment lengths after digestion, which appears as restriction fragment length polymorphism on gels. For example, sickle cell GAG to GTG mutation destroys MstII site. VNTR and STR polymorphisms involve tandem repeat copy number, not restriction recognition changes, while ESTs represent transcribed sequences. Therefore SNPs commonly provide molecular basis for RFLP variation and linkage studies.