Silent mutation and third position

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Silent mutations primarily affect the third position of a codon due to the redundancy in the genetic code, where multiple codons can encode the same amino acid. The first two bases of a codon are critical for determining the specific amino acid, and changes in these positions typically result in a different amino acid, which can be harmful. In contrast, alterations at the third position often do not change the amino acid being encoded, allowing for silent mutations that do not impact protein function. Understanding the concept of "wobble base" in tRNA recognition further clarifies why these mutations are more frequently observed at the third position.
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I got this question in an exam. Why do silent mutations always affect the third position of a codon? I have no clue about it.
 
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SanjuktaGhosh said:
I got this question in an exam. Why do silent mutations always affect the third position of a codon? I have no clue about it.

A quick google gave me some information on this, have you had a look?
 
They don't always affect the third position, but they are definitely more common at the third position. Read up on how tRNAs recognize codons during translation.
 
The search keywords "wobble base" might help.
 
I'm sorry I didn't do my research properly before posting this question. @pinball1970

Thanks to both of you. @JonMoulton & @Ygggdrasil

I'll soon reply with an answer.
 
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SanjuktaGhosh said:
I got this question in an exam. Why do silent mutations always affect the third position of a codon? I have no clue about it.
Because the first two bases are necessary to specify the type of amino acid to be encoded. And they are both the same base. It wouldn't be silent if it was one of the first two bases because then it would be deleterious. Only the third base can change and you can still encode the same amino acid.
 

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