- Specification route
- 3.4.3
- Question bank
- 22 questions
- Course stage
- AS / Year 12
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22 standard questions. No sign-in required.
Practise Biology maths and data skills
Sessions use up to the requested number of available questions. Standard practice uses levels 1–5.
Sample questions
Why do not all base substitution mutations cause a change in the sequence of encoded amino acids?
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Multiple different triplets can code for the exact same amino acid.
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Answer: Because of the degenerate nature of the genetic code.
Due to the degenerate nature of the genetic code, not all base substitutions cause a change in the sequence of encoded amino acids.
Mutations in the number of chromosomes can arise spontaneously. What process during meiosis is responsible for this?
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This occurs when chromosomes fail to separate correctly during anaphase.
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Answer: Chromosome non-disjunction
Mutations in the number of chromosomes can arise spontaneously by chromosome non-disjunction during meiosis.
What is the final cellular product of a single diploid parent cell undergoing the complete process of meiosis?
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Meiosis is a reduction division that produces gametes.
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Answer: Four haploid daughter cells
The process of meiosis results in the formation of four haploid daughter cells from a single diploid parent cell.
During meiosis, which two processes ensure that the resulting daughter cells are genetically different from each other?
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These processes shuffle the existing maternal and paternal genetic material.
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Answer: Independent segregation of homologous chromosomes and crossing over between homologous chromosomes.
Genetically different daughter cells result from the independent segregation of homologous chromosomes and crossing over between homologous chromosomes.
A base deletion mutation occurs in a gene. Why is this typically more harmful than a base substitution mutation?
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Because the code is read in non-overlapping triplets, removing one letter shifts how every subsequent triplet is read.
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Answer: It causes a frame shift, altering the nature of all base triplets downstream from the mutation.
Gene mutations involve a change in the base sequence... and include base deletion and base substitution. A deletion causes a frameshift, whereas a substitution might only affect one triplet (or none, due to the degenerate code).
A substitution mutation changes a DNA triplet from $CTC$ to $CAC$. However, the resulting polypeptide functions perfectly normally. What is the most likely biological explanation?
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If the sequence of amino acids is identical despite a DNA change, the code must have multiple ways to 'say' the same thing.
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Answer: The genetic code is degenerate, so both triplets may code for the exact same amino acid.
Due to the degenerate nature of the genetic code, not all base substitutions cause a change in the sequence of encoded amino acids. Multiple triplets can code for the same amino acid.
Which of the following would be classified as a mutagenic agent?
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These are external factors that increase the base rate of genetic alteration.
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Answer: High-energy ionising radiation, such as X-rays.
Mutagenic agents can increase the rate of gene mutation. Examples include high-energy ionising radiation (X-rays, UV) and certain chemicals (carcinogens).
An organism has a diploid chromosome number of $2n = 8$. Assuming no crossing over occurs, how many different combinations of maternal and paternal chromosomes are possible in its gametes due to independent segregation?
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Use the formula $2^n$, where $n$ is the number of homologous pairs.
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Answer: $16$
The number of possible chromosome combinations from independent segregation is $2^n$, where $n$ is the haploid number. If $2n = 8$, then $n = 4$. Therefore, $2^4 = 16$.
Practise this topic
22 standard questions are available (levels 1–5). No sign-in required.