A 35-year-old bank clerk presents to your office for evaluation of fatigue. She has a 15-pack-year history of smoking and had rheumatic heart fever in childhood. On auscultation of her heart, the S2 sound is widely split; that is, it persists like that throughout the respiratory cycle. What is the most likely cause of the wide and fixed S2 split?

Step 1 review the imaginary strand of dna below. note the complementary base pairs. a g c a a t c c g t c t t g g t c g t t a g g c a g a a c c step 2 to begin replicating this strand of dna, draw the two sides of the strand separating. step 3 now, draw the free-floating bases linking up with the separate sides. remember to follow the rules of complementary base pairing. step 4 draw the two resulting dna strands.