Question

Consider the nucleotide sequence TGACTAACG- GCT. Transcribe this sequence into mRNA. Use the genetic code to translate it into a string of amino acids. Give an example of a point mutation, an insertion, a deletion, a frameshift mutation, a synonymous substi- tution, a nonsynonymous substitution, and a nonsense mutation. Which of your examples seem likely to dra- matically influence protein function? Which seem likely to have little effect? Why?

Answer 1

The nucleotide sequence TGACTAACG-GCT is transcribed into mRNA and then translated into a string of amino acids. Types of mutations, including point mutations, insertions, and deletions, have varying effects on protein function, with frameshift and nonsense mutations being highly detrimental.

Step-by-step explanation:

Transcribing and Translating DNA Sequences

To transcribe the nucleotide sequence TGACTAACG-GCT into mRNA, we replace thymine (T) with uracil (U) and complement the other bases accordingly to get the sequence ACUGAUUGC-CGA. Translation of this mRNA sequence into amino acids involves using the genetic code, which would produce a specific string of amino acids.

Types of Mutations and Their Impacts

A point mutation is an alteration of a single nucleotide, such as changing an adenine (A) to a guanine (G). This could be a silent, missense, or nonsense mutation, impacting the protein function to different extents.

An insertion is the addition of nucleotides, while a deletion is the removal. Both can cause frameshift mutations if not in multiples of three, severely affecting protein structure and function. An example of each type of mutation:

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• Point Mutation: Changing UUU to UCU could result in a different amino acid.
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• Insertion: Adding a nucleotide, shifting the reading frame, altering all subsequent codons.
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• Deletion: Removing a nucleotide, similarly shifting the reading frame and potentially introducing a premature stop codon.
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• Frameshift Mutation: Occurs due to insertion or deletion not in multiples of three, typically rendering the protein nonfunctional.
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• Synonymous Substitution: A silent change where the new codon codes for the same amino acid, likely having little effect on the protein.
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• Nonsynonymous Substitution: A missense change where the new codon codes for a different amino acid, possibly altering protein function.
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• Nonsense Mutation: Replaces an amino acid codon with a stop codon, resulting in a truncated and frequently nonfunctional protein.

Frameshift mutations and nonsense mutations are likely to have a dramatic influence on protein function, while synonymous substitutions are likely to have little effect.