Question

Imagine an operon that has three structural genes: gene 1 makes protein 1, gene 2 makes protein 2, and gene 3 makes protein 3. the genes are arranged physically in the operon in the order gene 1, gene 2, gene 3, and transcribed/translated in that order as well.

what would the effect be on production of protein 3 if there was a missense mutation in gene 1? would you get the same effect on production of protein 3 if there was a nonsense mutation in gene 1? explain your answer.

Answer 1

A missense mutation in gene 1 would not have a direct effect on the production of protein 3. A nonsense mutation in gene 1 would result in decreased production or absence of functional protein 3.

Step-by-step explanation:

If there is a missense mutation in gene 1 of the operon, it would result in a different amino acid being incorporated into the protein coded by gene 1. However, since gene 1 is transcribed and translated before genes 2 and 3, the missense mutation in gene 1 would not directly affect the production of protein 3. This is because protein 3 is synthesized after gene 1 has already been transcribed and translated. So, a missense mutation in gene 1 would not have a direct effect on production of protein 3.

If there is a nonsense mutation in gene 1, it would convert the codon encoding an amino acid in gene 1 into a stop codon. This would result in premature termination of translation, leading to the synthesis of a nonfunctional truncated protein from gene 1. Since gene 2 and gene 3 are located downstream of gene 1 in the operon and are transcribed and translated after gene 1, their production would also be affected. The nonsense mutation in gene 1 would result in decreased production or absence of functional protein 3.