QUESTION 84 (5 marks)
Three events occur in separate beetle populations: P gains a new allele after a DNA-copying error; Q receives breeding immigrants carrying an allele rare in the local population; R is founded by five beetles that happen to lack an allele common in their source population.
a) Identify the main evolutionary process in P, Q and R. [3 marks]
b) Explain which event can introduce a genuinely new allele sequence and distinguish it from movement of an existing allele. [2 marks]
Practice marking scheme
Answer
a) P: mutation; Q: gene flow; R: genetic drift/founder effect. b) Mutation can create a new sequence; gene flow brings an already existing allele into another population.
Working
A replication error can alter the DNA sequence and produce a new allele. Breeding immigrants transfer alleles between populations, changing a local gene pool by gene flow. A small founding sample may differ from its source by chance, producing a founder effect, a form of genetic drift. These processes have different origins even though each can change allele frequencies.
Marking criteria
- Identifies mutation for P. [1 mark]
- Identifies gene flow for Q. [1 mark]
- Identifies founder effect/genetic drift for R. [1 mark]
- Links mutation to a new DNA sequence. [1 mark]
- Distinguishes transfer of an existing allele from creation of a new one. [1 mark]
Practice question aligned to the current QCAA syllabus; review the worked solution and marking criteria.
View the QCAA syllabusCompare your working with the guide above.