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30.3 - Do first: Nonsense, Missense, and Silent Mutations

Last updated 11 months ago
10 questions
There are four kinds of mutations that can result from DNA base substition, deletion, and insertion:
  • Silent mutations do not affect the sequence of amino acids during translation.
  • Nonsense mutations result in a stop codon where an amino acid should be, causing translation to stop prematurely.
  • Missense mutations change the amino acid specified by a codon.
  • Frameshift mutations cause the “reading frame” of the codons to shift forwards or backwards. This can change the entire sequence of amino acids.
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This mutation stops translation of an amino acid because a stop codon was added.

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When the codons in mRNA shift backwards or forwards because of inserting or deleting a base. All of the amino acids translated may be incorrect

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When the changing of a DNA base does not affect the amino acid sequence during translation, this is called...

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When an amino acid is changed during translation.

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Which type of mutation is seen below?

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Which type of mutation is seen below?

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Which type of mutation is seen below?

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Which type of mutation is seen below?

Common mistakes and misconceptions

  • Amino acids are not made during protein synthesis. Some students think that the purpose of protein synthesis is to create amino acids. However, amino acids are not being made during translation, they are being used as building blocks to make proteins.
  • Mutations do not always have drastic or negative effects. Often people hear the term "mutation" in the media and understand it to mean that a person will have a disease or disfigurement. Mutations are the source of genetic variety, so although some mutations are harmful, most are unnoticeable, and many are even good!
  • Insertions and deletions that are multiples of three nucleotides will not cause frameshift mutations. Rather, one or more amino acids will just be added to or deleted from the protein. Insertions and deletions that are not multiples of three nucleotides, however, can dramatically alter the amino acid sequence of the protein.
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