Question

Bioengineers construct peptides with new functions by starting with a particular peptide, and then mutating the amino acid present at different positions. They then screen the resulting mutant peptide for the desired function. Suppose the starting peptide is 10 amino acids long. Recall there are 20 amino acids.

(a) How many peptides will need to be screened if the amino acids at positions four, five, and nine are all mutated? (b) If we consider all possible mutants for the amino acid at one position only, but this can be at any of the 10 positions, how many new peptides will need to be screened?

Answer 1

Solution a) There are total 10 amino acids in the given peptide, out of which specific 3rd, 5th and 9th are mutated. as we know that there are 20 amino acids, so out of 20 amino acids, changing one amino acid to any of the remaining 19 amino acids. so there would be 19 x 19 x 19 = 6859 possible peptides to screen.

b) In this case, there we will need to screen amino acid for each of 10 positions for the possible 19 mutations at each = 19 x 10 = 190. there would be possible 190 peptides to screen.