In the polymerase chain reaction (PCR)

In the polymerase chain reaction (PCR), the target DNA is denatured into single strands; each strand is then annealed to short, complementary primers.

, Cycle1 , 5'I'I'I'I'r'I'I'I'I'I'I'I'I'I'I'I'1'I'I'I'I'I'I'I'I'I'I'I'1'I'l'I'I'I'I'I'3 DNAtobe 3:IIIIIIIIIIlIIIIIIIIIIlII|||I|I||Il||5ramplified l 5m? 1. Denature DNA   (92—95°C) 3/||l|ll|ll|ll|l|ll||||||l|||l|ll||||| 5! , l , 5 3 2. Anneal primers . ,3r.l.|.Ll.|.L5r (454m) 5, 3,/Prlmers yWI—I—Ls'      5Illlllllllllllllllllllllllll lllllllll3, 5’ l 3’ 3'W5' a/Ws/ 3. Extend primers (65—75°C; product of the first cycle doubles Cycle 2 the number of DNA molecules) 5,I||Il||I|||I||Il||l||ll|lll||l|||ll| 3, 5mg 3'J.H.|.|.L5' 3'JJ.LLLL5' 5"n-rn-r3' 5"rrrr'rr3’ 3/.Ll.|.|.|.l.|.|.|.|.|.|.l.l.|.|.|.|.|.Ll—l.|.l.LLl—LLL5I yWJ—I—Ll—H—I—I—U—s/ Repeat Steps 1 and 2. l Denature strands and anneal primers 9m? 5'1Tn'rT'I'I'1'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'I'3’ 3'W5r ad.|.|.l.|.|.|.l.l.|.L|—l.|.|.l.|.l.|.l.l.|.|.L5r 5’111111'11-rn-m-rn-n-rrrrr3’ 5’1'n'rrrrr'm'rr'rrm'rr1'rm'rrm'3’ 3; I I5: 3rIlllllllllllllIllllllllllll lllllllll5r Repeat Step 3. Extend primers 20 cycles increases DNA copies by ~106 (product of the second cycle is four new DNA molecules)