The smallest possible mutation, point mutation where one...

Name: Problem 5, Chapter 5: Evolutionary Analysis: Global Edition
Uploaded: 2020-07-15T03:23:25-08:00
Duration: 4 min 38 s
Channel: Carlene Jimenez
Description: The smallest possible mutation, point mutation where one base pair is substituted for another, can have a variety of effects. Some mutations result in a synonymous substitution, others result in a nonsynonymous substitution, and some are nonsense mutations. Explain these mutations using examples not given in the chapter. What are their effects on the functions of the affected proteins?

The smallest possible mutation, point mutation where one base pair is substituted for another, can have a variety of effects. Some mutations result in a synonymous substitution, others result in a nonsynonymous substitution, and some are nonsense mutations. Explain these mutations using examples not given in the chapter. What are their effects on the functions of the affected proteins?

Key Concepts

Point Mutation

A point mutation is a change in a single nucleotide base in the DNA sequence. This type of mutation can be small yet significant, as it alters the genetic code at only one position. Depending on the location and context within the gene, point mutations may or may not affect the protein product, and they serve as a fundamental mechanism generating genetic diversity or causing genetic disorders.

Synonymous Substitution

A synonymous substitution is a specific type of point mutation where the change in the nucleotide does not alter the amino acid specified by the codon due to the redundancy in the genetic code. Although the protein’s primary structure remains unchanged, these mutations might still affect protein expression or folding by influencing mRNA stability, splicing, or the speed of translation.

Nonsynonymous Substitution

A nonsynonymous substitution is a point mutation that results in a change in the codon such that it encodes a different amino acid. This alteration can lead to changes in the structure and function of the protein, potentially affecting its activity, stability, or interaction with other molecules. The impact depends on the properties of the substituted amino acid and its role in the protein’s overall structure.

Nonsense Mutation

A nonsense mutation is a type of point mutation in which a codon that originally coded for an amino acid is changed to a stop codon. This premature stop signal truncates the protein, often leading to a loss of function because the shortened polypeptide may be unstable, nonfunctional, or subject to rapid degradation by the cell’s quality control mechanisms.

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