Practice question

In overlap extension strategy for introducing mutations, primer nomenclature reflects functional roles. Internal mutagenic primers Q2 and Q3 contain complementary nucleotide changes and produce overlapping mutated ends. Outer primers Q1 and Q4 anneal to termini of gene and provide flanking sequences for amplification of full-length construct. After first-round generation of two halves, second-round PCR uses Q1 and Q4 to drive extension of annealed fragments into complete mutated gene. Thus Q1 and Q4 act as flanking primers for second PCR, not as sequencing primers or enzymes.