AQA A-level Biology — Control of Gene Expression flashcards
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AQA A-level Biology topic 8: gene mutations, stem cells, transcription factors, epigenetics and RNAi, cancer, genome projects, recombinant DNA and PCR, DNA probes and screening, and genetic fingerprinting.
Learn deck · part of AQA A-level Biology · written against: AQA AS and A-level Biology (7401/7402) specification, version 1.6, July 2026 (eight topics). Updated 2026-10-10.
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Which six types of gene mutation does the AQA course name?Addition, deletion, substitution, inversion, duplication and translocation of bases.Control of Gene Expression › Gene Mutation
Any of them can happen by chance when DNA is copied, and mutagens make them more frequent. -
How does an inversion mutation change a polypeptide?A section of bases is reversed, so the triplets in that section change and several amino acids in that region may change.Control of Gene Expression › Gene Mutation
Triplets outside the inverted section are unaffected, so there is no frame shift. -
What is a translocation of bases?A section of bases moves from one location to another, on the same chromosome or a different one.Control of Gene Expression › Gene Mutation
It can disrupt the gene it leaves and the gene it enters. -
Why does the addition of a single base usually have a large effect on the polypeptide?It causes a frame shift: every triplet downstream of the addition is changed.Control of Gene Expression › Gene Mutation
Many amino acids change, and a premature stop codon may appear. -
Why is deleting three adjacent bases often less harmful than deleting one?Removing three bases takes out one triplet's worth, so there is no frame shift; usually just one amino acid is lost.Control of Gene Expression › Gene Mutation
If the deletion spans two triplets, the amino acid beside it may also change. Deleting one base shifts the reading frame for the rest of the gene. -
A substitution changes a triplet into a stop triplet partway through a gene. What is the effect?Translation stops early, giving a shorter polypeptide that is usually non-functional.Control of Gene Expression › Gene Mutation
The tertiary structure cannot form properly without the missing amino acids. -
A duplication adds two extra copies of a single base. Why does this cause a frame shift?Two extra bases is not a multiple of three, so every triplet after the duplication is read differently.Control of Gene Expression › Gene Mutation
Duplicating a whole triplet would add an amino acid without a frame shift. -
What is a totipotent cell, and where is it found in mammals?A cell able to give rise to every cell type in the body; in mammals such cells exist only briefly, in the very early embryo.Control of Gene Expression › Totipotency and Stem Cells
Totipotent cells can also form the cells of the placenta. -
How do cells become specialised if they all carry the same DNA?During development only part of each cell's DNA is translated: different genes are switched on in different cells.Control of Gene Expression › Totipotency and Stem Cells
The proteins made decide the cell's structure and function. -
How do pluripotent, multipotent and unipotent stem cells differ?Pluripotent (in embryos) can form almost any cell type; multipotent (in adults) a limited number of types; unipotent only one type.Control of Gene Expression › Totipotency and Stem Cells
Example: AQA's example of a unipotent cell is one that can form only cardiomyocytes (heart muscle cells).
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About these cards
Review status: Second-reader reviewed, with corrections applied.
Checked against:
- Topic outline follows the AQA AS and A-level Biology (7401/7402) specification, version 1.6 (July 2026) (outline only; no specification text reproduced).
- OpenStax Biology 2e, consulted as a reference; no text copied.
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