Practise 35 exam-style questions on Selective breeding for AQA GCSE Biology. Write your answer as you would in the exam and get it marked in seconds against the mark scheme, point by point, with an AI tutor on hand if you get stuck.
35 questions
2–6 marks each
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20 questions, marked as you go
Sample questions with model answers
Here are 4 of the questions in this topic, each with a model answer, an explanation of why it earns the marks and the mark scheme an examiner would use.
Question 1
2 marks
Name one crop and one animal that have been improved by selective breeding.
Model answer
Crop: wheat (higher yield) or maize. Animal: dairy cow (higher milk yield) or broiler chicken (faster growth).
Explanation
Selective breeding has produced higher-yielding crops (e.g., wheat, maize) and farm animals selected for milk, meat, or egg production (e.g., dairy cattle, broiler chickens).
Mark scheme
1 mark
named crop eg wheat, maize, rice
1 mark
named animal eg dairy cow, broiler chicken, pig, sheep
Question 2
3 marks
Describe one reason why pedigree recording/family records are useful in a selective-breeding programme.
Model answer
Pedigree records show which individuals carry desirable traits and allow tracking of inheritance, helping avoid mating close relatives and identifying carriers of recessive conditions.
Explanation
Pedigrees allow breeders to follow traits through generations and make informed mating decisions to enhance desired traits while minimising inbreeding and inherited disorders.
Mark scheme
1 mark
tracks which individuals have desirable traits
1 mark
helps avoid close inbreeding / identify relatives
1 mark
helps identify carriers of recessive diseases by looking at family history
Question 3
4 marks
A breeder chooses a bull with desirable milk-gene allele 'M' and mates with many cows. Describe the genetic effect on allele frequency and why this is an effective strategy.
Model answer
Using one bull to father many offspring increases the contribution of 'M' to the next generation, increasing its allele frequency. It's effective because it amplifies the chosen allele quickly across the herd.
Explanation
Using a single high-quality sire concentrates its alleles in the next generation; if that sire has the desired allele, its frequency rises rapidly, making breeding efficient.
Mark scheme
1 mark
bull fathers many offspring increasing transmission of allele M
1 mark
allele frequency of M increases in population
1 mark
strategy spreads desired allele quickly
1 mark
effective because many offspring share same father (high reproductive success)
Question 4
5 marks
A plant breeder crosses two varieties A and B. Offspring have a range of heights with some taller than both parents. Explain how this could occur genetically.
Model answer
The parents may carry different alleles at height genes. Recombination during sexual reproduction produces new allele combinations; some offspring inherit alleles that together give taller height (additive or epistatic effects), producing transgressive segregation where extremes exceed parents.
Explanation
Crossing diverse parents mixes alleles; recombination can create offspring with allele combinations that give more extreme traits than parents, such as greater height.
Mark scheme
1 mark
parents have different alleles for height
1 mark
recombination produces new allele combinations in offspring
1 mark
some combinations lead to taller height than either parent (additive/epistasis)
1 mark
this is transgressive segregation / extremes in offspring
1 mark
sexual reproduction mixes genes so new phenotypes appear
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