QUESTION 145 (6 marks)
Complete genotype counts are shown for two breeding populations. Ten AA adults move from P to Q and join Q’s breeding population. No birth, death, mutation or other movement occurs.
| Population | AA | Aa | aa |
|---|---|---|---|
| P | 30 | 40 | 30 |
| Q | 10 | 20 | 70 |
a) Calculate A frequency in each population after movement, to three decimal places. [3 marks]
b) Determine whether the combined A frequency of the two populations changes. Justify using allele totals. [2 marks]
c) Name the evolutionary process affecting the local gene pools. [1 mark]
Practice marking scheme
Answer
After movement, f(A) is 0.444 in P and 0.273 in Q. Across both populations combined it remains 0.350. This is gene flow; existing alleles change location without changing the regional allele total.
Working
After transfer, P has 20 AA, 40 Aa and 30 aa: 80 A copies among 180. Q has 20 AA, 20 Aa and 70 aa: 60 among 220. Combined counts remain 140 A among 400 alleles, giving 0.35. Local gene pools change even though the combined regional count does not.
Marking criteria
- Uses post-movement genotype counts correctly. [1 mark]
- Calculates P frequency 80/180 = 0.444. [1 mark]
- Calculates Q frequency 60/220 = 0.273. [1 mark]
- States combined frequency remains 0.350. [1 mark]
- Uses conserved totals 140 A copies and 400 alleles. [1 mark]
- Identifies gene flow. [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.