A gene has two alleles. A cross between two heterozygous individuals gives 120 offspring. How many would you expect to be homozygous recessive?
Answer and explanation
Correct answer: C. 30
- Step 1: Cross Aa × Aa gives 1 AA : 2 Aa : 1 aa.
- Step 2: are aa.
Answer
30.
Why not the others: 60: this is the number of heterozygotes. 90: this is the number showing the dominant phenotype. 120: this is the total.
Practise more Ecology, Evolution and Immunity.
Free questions with an explanation for every one, and full timed Scottish Highers mock tests.
More Ecology, Evolution and Immunity questions
- Why is the energy transfer between trophic levels in a food chain usually low?
- A producer fixes 12000 kJ of energy. The primary consumer receives 1200 kJ. What is the percentage efficiency of energy transfer?
- Which of the following is a density-dependent factor affecting a population?
- What is meant by biodiversity?
- Isolation of populations can lead to speciation. What is the term for speciation caused by a geographical barrier?
- Which statement describes stabilising selection?