How many different polypeptides of 50 amino acids in length can be made from the 20 common amino acids?

Answer: 20^50

Explanation:

A protein or polypeptide is a long chain of different amino acids covantently linked together with a peptide bond.

If we have 20 differents amino acids, and you want to generate a protein or a short peptide of just 2 amino acids we can generate 20 * 20 = 400 different proteins having different amino acids combination. It can also be represented as 20^2 = 400

So also generating a short peptide of 3 distinct amino from 20 amino acids monomers we get 20^3 = 8000 distinct proteins.

So 20^n proteins can be made from 20 different amino acids.

Therefore making a protein on 50 amino acids long from 20 different amino acids, we get 20^50 distinct proteins.

Answer is 20^50