Hardy-Weinberg and speciationEdexcel A-Level Biology A: Flashcards

Exam questions on Hardy-Weinberg and speciation

1. A population of 1000 moths shows two phenotypes controlled by one gene with two alleles. The allele B for dark wings is dominant and the allele b for pale wings is recessive. The frequency of allele b is 0.3. The population is assumed to be in Hardy-Weinberg equilibrium.
   Calculate the number of pale moths expected in the population.2 marks
2. A population of about 60 wildflowers grows on a hillside. Seeds fall close to the parent plant, so plants mostly breed with near neighbours. A genetic screen showed that the frequency of allele R of one gene fell from 0.62 to 0.55 over two years. No plants arrived from elsewhere and no new alleles were found.
   Hardy-Weinberg equilibrium also requires no selection and a large population. Suggest how each of these conditions may have been broken in this population.2 marks
3. A recessive genetic disorder affects 1 in 10 000 babies in a large population that is assumed to be in Hardy-Weinberg equilibrium. The frequency of the dominant allele is p and the frequency of the recessive allele is q. A health authority wants to estimate how many people in a city of 2 000 000 carry the disorder allele without having the disorder.
   Calculate the frequency of the dominant allele and of the recessive allele. Show your working.3 marks