AP BIOLOGY

Detailed explanation-1: -How many different kinds of polypeptides, each composed of 12 amino acids, could be synthesized using the 20 common amino acids? The book’s answer is 2012.

Detailed explanation-2: -Since each of the 20 amino acids is chemically distinct and each can, in principle, occur at any position in a protein chain, there are 20 × 20 × 20 × 20 = 160, 000 different possible polypeptide chains four amino acids long, or 20n different possible polypeptide chains n amino acids long.

Detailed explanation-3: -Therefore making a protein on 50 amino acids long from 20 different amino acids, we get