Genetic variants in coding DNASpec 3.10B
Variants in the coding DNA of a gene can change the base sequence that codes for the protein.
- A variant in the coding DNA can alter the sequence of amino acids.
- The polypeptide may then fold into a different shape.
- A protein with a different shape may have different activity. For example, an enzyme's active site may no longer fit its substrate.
- The change in the activity of the protein can affect the phenotype.
| Where the variant is | What changes | Effect on phenotype |
|---|---|---|
| Non-coding DNA in front of the gene | Binding of RNA polymerase | Quantity of protein produced is altered |
| Coding DNA of the gene | Sequence of amino acids | Activity of the protein produced is altered |
Quick check
What decides the order of amino acids in a protein?
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The order of bases in a section of DNA (the gene).
What does RNA polymerase do?
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It binds to non-coding DNA in front of a gene and produces a complementary mRNA strand from the coding DNA.
What is a codon?
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A triplet of bases in mRNA that codes for a specific amino acid.
What carries amino acids to the ribosome?
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tRNA.
How can a variant in non-coding DNA affect phenotype?
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It can change the binding of RNA polymerase and so alter the quantity of protein produced.