Practice question

Double-stranded DNA consists of sense coding strand identical to mRNA and antisense template strand. Forward primer is designed to be identical to sense strand sequence but complementary to antisense strand, thereby annealing to antisense strand and directing synthesis of sense strand copy. Reverse primer anneals to sense strand. Together they flank target region in opposite directions, permitting exponential amplification. Binding to DNA-RNA hybrid is irrelevant for conventional PCR. Understanding strand polarity is crucial for directional cloning, expression studies, and primer design in molecular biology examinations.