A)PCR reaction contains DNA template,primers,deoxyribonucleotide triphosphates,and heat-resistant DNA polymerase.
B)Each PCR cycle includes three steps: denaturation,annealing,and extension.
C)After each PCR cycle,amount of DNA increases in a linear manner.
D)One limitation in PCR is that it requires prior knowledge of the sequence or at least part of the sequence to be amplified.
E)PCR is a very sensitive technique and can amplify target sequences present in extremely low copy numbers.

A)anneal to the same strand of template DNA,though at distant sites.
B)anneal to opposite strands of template DNA at distant sites,with their 3′ ends directed toward each other.
C)anneal to opposite strands of template DNA at distant sites,with their 5′ ends directed toward each other.
D)anneal to each other to prime DNA polymerization.
E)hybridize only to DNA within the open reading frame of a selected gene.

A)cDNAs are generally copies of mRNA from expressed genes.
B)Reverse transcriptase activity is required for cDNA cloning.
C)cDNA clones lack exons,as introns are spliced together before cloning.
D)cDNAs are typically smaller than the chromosomal sequence for a particular gene.
E)cDNAs can be fused to a promoter to enable expression of the encoded gene.