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 molecule weight of each amino acid is $90Da$.

• A. $510$
• B. $663$
• C. $123$
• D. $170$

Answer 1

The correct option is A $510$

Since the molecular weight of the DNA polypeptide is 15.3 kDa. This is equal to 15300 daltons. Since the molecule weight of each amino acid is assumed to be 90, the number of amino acids in the polypeptide sequence is

$\frac{15300}{90}=170$ amino acids.

As one amino acid codes for 1 codon, and 1 codon is made of 3 nucleotides

$170\times 3=510$.

Thus the correct answer is option A.