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Chapter 12: Problem 60

What is a silent mutation? Why is the name "silent mutation" a bit of a misnomer?

Short Answer

Expert verified
A silent mutation is a DNA change that does not alter the amino acid sequence of a protein. The term 'silent' is misleading because such mutations can still affect protein function in other ways.

Step by step solution

01

Define Silent Mutation

A silent mutation is a change in the nucleotide sequence of DNA that does not alter the amino acid sequence of the protein produced. This usually occurs due to the redundancy of the genetic code, where different codons can encode the same amino acid.
02

Explain Codon Redundancy

The genetic code is redundant, meaning that multiple codons can correspond to the same amino acid. For example, the codons GAA and GAG both encode for the amino acid glutamic acid. Hence, a mutation from GAA to GAG would not change the resulting amino acid.
03

Explain Why 'Silent' is a Misnomer

The term 'silent mutation' can be misleading because although the primary structure of the protein (its amino acid sequence) remains unchanged, other properties might be affected. This includes the speed of translation, mRNA stability, and protein folding. Thus, these mutations can have functional consequences beyond the amino acid sequence.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Silent Mutation
A silent mutation occurs when there is a change or alteration in the DNA nucleotide sequence that does not result in a change in the amino acid sequence of a protein. This type of mutation happens because of the redundancy in the genetic code. Silent mutations are called 'silent' because they do not change the primary structure of the protein.
The term 'silent mutation' might seem a bit misleading. Even if the amino acid sequence stays the same, other factors like translation speed, mRNA stability, and protein folding could still be impacted. So, these 'silent' changes are not always entirely without effect.
DNA Nucleotide Sequence
The DNA nucleotide sequence refers to the order of nucleotides (the building blocks of DNA) in a DNA molecule.
Nucleotides are made up of three parts: a sugar molecule, a phosphate group, and a nitrogenous base (adenine, thymine, cytosine, or guanine). These bases pair specifically (adenine-thymine and cytosine-guanine) to form the double helix structure of DNA.
Changes in this nucleotide sequence can result in mutations. Think of mutations as 'edits' in the DNA sequence. If these changes occur in essential regions, they can affect how proteins are made and how they function.
Codon Redundancy and Genetic Code
  • The genetic code is like the 'dictionary' that translates DNA sequences into amino acids, the building blocks of proteins.

This code is read in sets of three nucleotides called codons. Each codon corresponds to a specific amino acid.
Due to codon redundancy, several different codons can code for the same amino acid. For example, the codons GAA and GAG both encode for glutamic acid.
This redundancy means that a change in one nucleotide of a codon might still result in the same amino acid being produced, which is why certain mutations are 'silent.'
Hence, the genetic code's redundancy is a protective feature, reducing the chance that a mutation will affect protein function.

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Most popular questions from this chapter

The nucleoside inosine frequently occurs as the third base in codons. What role does inosine play in wobble base pairing?

In the early days of research on protein synthesis, some scientists observed that their most highly purified ribosome preparations, containing almost exclusively single ribosomes, were less active than preparations that were less highly purified. Suggest an explanation for this observation.

It is possible for the codons for a single amino acid to have the first two bases in common and to differ in the third base. Why is this experimental observation consistent with the concept of wobble?

A genetic code in which two bases encode a single amino acid is not adequate for protein synthesis, Give a reason why.

What role does ubiquitin play in the degradation of proteins?
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