Igcse Model Questions Vol1 2017 Biology Question 10

Practice essay / theory question 10 from the 2017 Igcse Model Questions Vol1 Biology examination. This question covers Population Genetics, Hardy–Weinberg equilibrium, Mutation, Selective breeding .

Igcse Model Questions Vol1 2017 Biology Essay / Theory
Topics: Population Genetics Hardy–Weinberg equilibrium Mutation Selective breeding
Question 10 IGCSE_MODEL_QUESTIONS_VOL1 • 2017 • BIOLOGY • essay

In a population of a freshwater fish, scale colour is controlled by a single gene with two alleles: S (dominant, silver) and s (recessive, black). A random sample of 200 fish shows 120 silver and 80 black individuals. The fish breed randomly.

Question Parts

( a )
Using Hardy–Weinberg principles, estimate the frequencies of the S and s alleles in this population.
( b )
Predict the expected genotype frequencies (SS, Ss, ss) in the next generation if the population remains in Hardy–Weinberg equilibrium.
( c )
A mutation occurs that converts the S allele to a new dominant allele T (gold) at a rate of 1 × 10⁻⁵ per generation. Assuming no selection, discuss the likely impact of this mutation on allele frequencies over 100 generations.
( d )
A breeder decides to select only silver‑coloured fish (SS or Ss) for breeding. Explain how this selective breeding will affect the allele frequencies of S and s over successive generations.

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About This Question

This is Igcse Model Questions Vol1 2017 Biology Question 10. It is one of the essay questions from the 2017 Igcse Model Questions Vol1 Biology examination.

The question covers Population Genetics, Hardy–Weinberg equilibrium, Mutation, Selective breeding .

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