Selective breeding — AQA GCSE Biology
Test yourself on Selective breeding with AQA GCSE practice questions.
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Selective breeding explained
Selective breeding is not a single event; it is a repeated cycle.
Read the full explanation
In each generation the breeder selects individuals showing the desired characteristic and breeds them together. Because those parents are more likely to carry the favourable alleles, more of their offspring show the trait. Repeating the cycle over many generations steadily raises the frequency of the favourable alleles in the population. Eventually, if selection is strong and the trait is reliably inherited, nearly all offspring show the desired characteristic, producing a breed or variety that breeds true for that trait. In practice, complete uniformity may take many years and can be limited by genetic variation, environmental effects and the appearance of inherited problems.
Your focus
- Describe the repeated cycle of selection and breeding over many generations.
- Explain how allele frequencies change across generations of selective breeding.
- State the endpoint of selective breeding as a population in which all offspring show the desired characteristic.
Selective breeding exam tips
Marking Points
- Selective breeding is a repeated cycle carried out over many generations.
- Each generation involves selecting individuals with the desired characteristic and breeding them together.
- The frequency of favourable alleles in the population increases across generations.
- The proportion of offspring showing the desired characteristic rises over time.
- The endpoint is a population in which essentially all offspring show the desired characteristic.
- The process can take many generations and may be limited by remaining variation or inherited defects.
Examiner Tips
- 💡Use the phrase ‘over many generations’ to show understanding of the timescale.
- 💡Explain the endpoint as a population in which all offspring show the desired characteristic.
- 💡Link the increase in offspring showing the trait to the increased frequency of favourable alleles.
Common Mistakes
- Believing that all offspring show the desired characteristic after one generation; the correction is that many generations of selection are usually needed.
- Thinking that selection changes an individual’s genes during its lifetime; the correction is that selection changes which alleles are passed on to the next generation.
- Assuming the process always produces a perfect result; the correction is that inbreeding and remaining variation can prevent complete uniformity.