Review of Lessons 1 to 7. This checkpoint covers mutation as the source of new alleles, mutagens, point and chromosomal mutation, somatic vs germ-line significance, coding vs non-coding DNA, variation from meiosis and fertilisation, and population-level gene pool change.
Mutation vs allele reshuffling, mutagen vs mutation, radiation, chemical and natural mutagens.
Point mutation, silent/missense/nonsense, frameshift logic, deletion, duplication, inversion and translocation.
Somatic vs germ-line mutation, coding vs non-coding DNA, inheritance relevance and regulatory significance.
Mutation, meiosis and fertilisation as different sources of variation.
Gene pools, mutation, gene flow and genetic drift, including founder effect and bottleneck reasoning.
1. Which process is the direct source of a new allele in a population?
2. Which statement best distinguishes a mutagen from a mutation?
3. A one-base insertion changes every codon after the mutation site. This is best explained as
4. Which chromosomal mutation involves movement of a chromosome segment to a different chromosome?
5. Why can a mutation in non-coding DNA still be significant?
6. Which mutation type is normally able to enter the next generation?
7. Siblings differ genetically even without new mutation mainly because of
8. What is the main effect of gene flow on a gene pool?
9. A rare allele becomes common in a very small isolated population after a founder event, even though it offers no clear advantage. This is best explained by
10. Which statement is the best evaluation of mutation, gene flow and genetic drift in changing populations?
11. Explain why mutation is considered the source of new alleles, while meiosis and fertilisation are not. 4 marks
12. Compare the significance of a somatic coding mutation, a germ-line coding mutation, and a germ-line non-coding mutation. 5 marks
13. Evaluate why genetic drift may have a stronger short-term effect than mutation in a small isolated population, even though mutation is essential in the long term. 6 marks
1. C - Mutation is the direct source of new alleles.
2. B - A mutagen increases mutation risk, while a mutation is the DNA sequence change itself.
3. A - A one-base insertion can cause frameshift and change downstream codons.
4. D - Translocation moves a chromosome segment to a new chromosome location.
5. C - Non-coding DNA can still be important because some regions regulate gene expression.
6. B - Germ-line mutations are the ones normally able to enter the next generation.
7. A - Sibling differences usually arise through meiosis and fertilisation reshuffling existing alleles.
8. D - Gene flow moves alleles between populations.
9. C - Founder effect is a form of genetic drift.
10. B - The best evaluation is scenario-based and distinguishes the roles of each process.
Q11 (4 marks): Mutation is considered the source of new alleles because it changes the DNA sequence itself [1]. This can produce a gene variant not previously present in the population [1]. Meiosis does not usually create new alleles; it reshuffles existing alleles through independent assortment and crossing over [1]. Fertilisation also does not create new alleles; it combines gametes randomly to create new allele combinations in offspring [1].
Q12 (5 marks): A somatic coding mutation may change a protein in body cells and affect the individual, but it is not normally inherited [1]. A germ-line coding mutation can be inherited and may directly alter protein sequence in offspring [1]. A germ-line non-coding mutation can also be inherited [1]. Although it may not alter amino acid sequence directly, it can still affect gene regulation or expression [1]. Therefore significance depends on both whether the mutation is inherited and whether it affects protein sequence or gene regulation [1].
Q13 (6 marks): Genetic drift may have a stronger short-term effect than mutation in a small isolated population because chance events can rapidly change allele frequencies from one generation to the next [1]. In small populations, random survival and reproduction have a much larger proportional effect [1]. Founder effects and bottlenecks are strong examples of this [1]. Mutation is still essential because it is the source of genuinely new alleles entering the gene pool [1]. However, mutation alone often changes frequency more slowly than strong drift [1]. Therefore drift may dominate short-term allele-frequency change in small isolated populations, even though mutation remains essential for long-term genetic novelty [1].
Tick this once you have finished the multiple choice, self-marked the short answers and reviewed the model responses.