Answer:
(a) 2.5 residues
(b) 10 residues
Explanation:
The amino acid substitution rate is a measure of evolutionary change for a given taxonomic group, species, etc. In general, this value is accompanied by a unit of time (often, the number of generations in prokaryotic organisms).
1 codon = 1 amino acid
Error rate >> 5 × 10−4 per codon = 50/ 10,000 (i.e. 50 amino acid substitutions per 10,000 residues)
500 residues >> (500 x 50)/ 10,000 = 2.5 residues
2000 residues >> (2,000 x 50)/ 10,000 = 10 residues