AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
(HT only) Students should be able to explain how a change in DNA structure…
Full specification wording
DNA structure (biology only): (HT only) Students should be able to explain how a change in DNA structure may result in a change in the protein synthesised by a gene.
A change in DNA structure means a change in the base sequence of a gene.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 10 of 19
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A change in DNA structure means a change in the base sequence of a gene. Because the base sequence is read in sets of three to specify amino acids, altering it can change the amino acids inserted into the protein. A substitution may change one amino acid, while an insertion or deletion can shift the reading frame so that many amino acids after the change are different. The altered amino acid sequence can change how the protein folds, which may change its shape and therefore its function. For example, a changed active site may no longer bind its substrate. The result is a different protein synthesised by that gene, which may affect the phenotype.
What earns the marks
- A change in DNA structure is a change in the base sequence of a gene.
- The base sequence is read in triplets, each triplet coding for one amino acid.
- A substitution can change one amino acid, while insertion or deletion can shift the reading frame and change many amino acids.
- A changed amino acid sequence can alter the folding and shape of the protein.
- A protein with a changed shape may have altered function, which can affect the phenotype.
Common mistakes and how to put them right
Saying a change in DNA always changes the protein.
Put it right by noting that some changes do not alter the amino acid sequence or protein function.
Confusing the effect of substitution with insertion or deletion.
Put it right by explaining that insertion or deletion can shift the reading frame.
Thinking the protein is made directly from DNA without a messenger copy.
Put it right by including the role of the messenger copy in carrying the code to the ribosome.
Exam tips
- Structure your answer as a chain: base sequence change, amino acid change, protein shape change, function change.
- Name the type of mutation and state its likely effect on the reading frame.
- Use a specific example, such as an enzyme active site, to show how shape affects function.
Try the lesson
The start of the DNA structure (biology only): (HT only) Students should be able to explain how a change in DNA structure may result in a change in the protein synthesised by a gene. lesson, made from checked teaching notes for this specification point.
Have a go first
A mutation changes the base sequence of a gene. What is the direct effect of this change on the protein made from that gene?
Listen
A change in DNA structure means a change in the base sequence of a gene. Because the base sequence is read in sets of three to specify amino acids, altering it can change the amino acids inserted into the protein. A substitution may change one amino acid, while an insertion or deletion can shift the reading frame so that many amino acids after the change are different. The altered amino acid sequence can change how the protein folds, which may change its shape and therefore its function. For example, a changed active site may no longer bind its substrate. The result is a different protein synthesised by that gene, which may affect the phenotype. A strong answer earns marks for these points. A change in DNA structure is a change in the base sequence of a gene. The base sequence is read in triplets, each triplet coding for one amino acid. A substitution can change one amino acid, while insertion or deletion can shift the reading frame and change many amino acids. A changed amino acid sequence can alter the folding and shape of the protein. A common slip: Saying a change in DNA always changes the protein. Instead, noting that some changes do not alter the amino acid sequence or protein function. Exam tip: Structure your answer as a chain: base sequence change, amino acid change, protein shape change, function change.
See it
Key words
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The genetic code as triplets
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Mutations and reading frames
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Protein folding and function
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From genotype to phenotype
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See every definition
- The genetic code as triplets
- The base sequence is read in triplets, each triplet coding for one amino acid.
- Mutations and reading frames
- A substitution can change one amino acid, while insertion or deletion can shift the reading frame and change many amino acids.
- Protein folding and function
- A changed amino acid sequence can alter the folding and shape of the protein, and a protein with a changed shape may have altered function.
- From genotype to phenotype
- A different protein synthesised by that gene may affect the phenotype.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
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