Question

In a translation experiment, two different mRNAs with different nucleotide sequences used are as follows:

mRNA 1:

5' AUG UUU UUA UUU UUA UAA UUC UUG - 3' and

mRNA 2:

5' AUG UUC UUG UUA UUU UAG UUU UUA CUU - 3'

From the following identify the TRUE statement.

Options

• Both mRNAs code for polypeptides having same molecular weight.

• Molecular weight of the two polypeptides coded by both mRNAs cannot be compared.

• mRNA 2 codes for high molecular weight polypeptide than mRNA 1.

• mRNA 1 codes for high molecular weight polypeptide than mRNA 2.

Answer 1

Both mRNAs code for polypeptides having same molecular weight.

Explanation:

The following is the translation product of two mRNA strands:

mRNA 1-met-phe-leu-phe-leu-stop

mRNA 2-met-phe-leu-leu-leu-phe-stop

Both strands have a stop codon at the sixth position, UAA and UAG, respectively, which inhibits protein synthesis after the addition of the fifth amino acid, and both strands have the same amino acids in polypeptides. As a result, both mRNAs code for the same molecular weight polypeptide.