Question

If molecular weight of a polypeptide is $15.3kDa$, what would be the minimum number of nucleotides in the mRNA that codes for this polypeptide? Assume that molecular weight of each amino acid is $90Da$.

• A. 510
• B. 663
• C. 123
• D. 170

Answer 1

Answer: (A)

Molecular weight of polypeptide $=15.3kDa$
Molecular weight of amino acid $=90Da$
$\therefore$ Number of amino acids in polypeptide
$=\frac{15.3\times 10^3}{90}=170$
We have one amino acid coded by three nitrogen base
$\therefore 170$ amino acids would be coded by
$170\times 3=510$ nitrogen bases.