A particular E. coli gene codes for mRNA containing 900 bases which is translate

Question

A particular E. coli gene codes for mRNA containing 900 bases which is translated into a 40 kD protein. A mutant from of the gene created by a single point mutation also yields a 900-base mRNA but only a 37 kD protein. What is the most likely effect of the mutation on the genetic code of the gene?

A. The E site of the ribosome has been altered preventing entry of charged tRNA.

B. Valine codons have been changed to glycine codons. The size is smaller than valine.

C. A TTG sequence in the middle of the gene was changed to ATG, creating a new transcription start site resulting in a smaller protein.

D. An amino acid coding codon was changed to a stop codon causing premature termination of translation.

E. Unregulated EF-Tu hydrolysis of GTP after dissociation from the aminoacyl-tRNA bound in the site A site results in smaller proteins.

Explanation / Answer

D. An amino acid coding codon was changed to a stop codon causing premature termination of translation.

A single point mutation from TTG to TAG would have substituted Leu with a stop codon which results in the premature termination of protein

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