The enzyme thanksgivingase in wild type E. coli converts cranberry sauce into a

Question

The enzyme thanksgivingase in wild type E. coli converts cranberry sauce into a number of poisonous byproducts in the intestinal tracts of humans. This enzyme is extremely unusual in that it consists of only four amino acids: alanine, arginine, methionine, and proline. Fortunately, the E. coli living in our colons is a mutant strain in which a single nucleotide has been changed in the thanksgivingase gene. This single base change has created a stop codon in the middle of the gene, resulting in a shortened form of the enzyme, which is completely inactive. (Many lives are saved every November as a result)

A. Did this mutation occur in an alanine, arginine, methionine, or proline codon?

B. What is the sequence of the stop codon created by this mutation?

Explanation / Answer

A. Alanine can be coded by the codons - GCU, GCC, GCA, GCG.

Arginine can be coded by the codons - CGU, CGC, CGA, CGG, AGA, AGG

Methionine is coded by the codon - AUG

Proline can be coded by the codons - CCU, CCC, CCA, CCG.

Stop codons are - UAG, UAA, UGA.

The mutation has occurred in arginine codon - AGA.

B. The mutation has converted the arginine codon AGA to UGA which is a stop codon.

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