Question

A cDNA was synthesized from the mRNA of a eukaryotic gene. After cloning and sequence analysis, the double-stranded cDNA of 614 bp revealed 125 bp 5'-UTR and 120 bp 3'-UTR. The number of amino acids present in the polypeptide encoded by this gene is ............... (answer in integer)

Hint:

To calculate the number of amino acids encoded by a gene, first subtract the UTR regions from the total cDNA length to get the coding region, then divide by 3 to account for the codon length.

Answer 1

Step 1: Understanding the problem. We are given a cDNA of 614 base pairs (bp) that includes 125 bp 5'-UTR and 120 bp 3'-UTR. The coding region (which codes for the polypeptide) will be the remaining part of the cDNA after subtracting the UTR regions. \[ \text{Length of coding region} = 614 \, \text{bp} - 125 \, \text{bp (5'-UTR)} - 120 \, \text{bp (3'-UTR)} = 369 \, \text{bp} \] Step 2: Converting the coding region length to amino acids. Each codon consists of 3 base pairs, and each codon codes for one amino acid. To find the number of amino acids, divide the length of the coding region by 3: \[ \text{Number of amino acids} = \frac{369}{3} = 123 \] Final Answer: \[ \boxed{123} \]