AQA · GCSE · Biology
Course version: 8461 · Version from Sept 2018
Selective breeding can lead to ‘inbreeding’ where some breeds are…
Full specification wording
Selective breeding: Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects.
Repeatedly breeding together individuals that show the same desired characteristic reduces genetic variation in the population.
Checked against the AQA 8461 specification (opens in a new tab) on .
- Point 9 of 9
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
Repeatedly breeding together individuals that show the same desired characteristic reduces genetic variation in the population. If closely related individuals are bred, the population becomes inbred. Inbreeding increases the chance that harmful recessive alleles are inherited from both parents, so offspring may show inherited defects. It also reduces the ability of the population to adapt to new diseases or environmental changes, so some breeds become particularly prone to disease. Examples include certain dog breeds with inherited breathing or joint problems and some crop varieties that are vulnerable to a new pathogen. Breeders may reduce the risk by introducing unrelated individuals to restore variation.
What earns the marks
- Selective breeding can reduce genetic variation within a breed or variety.
- Inbreeding occurs when closely related individuals are bred together.
- Inbreeding increases the chance of offspring inheriting harmful recessive alleles from both parents.
- Inbred breeds may be particularly prone to disease or inherited defects.
- Reduced genetic variation makes a population less able to adapt to new diseases or environmental changes.
- Breeders can reduce inbreeding by introducing unrelated individuals to increase genetic variation.
Common mistakes and how to put them right
Thinking that selective breeding always improves health.
Put it right: It can increase the risk of inherited defects.
Confusing inbreeding with selective breeding itself.
Put it right: Inbreeding is a consequence of breeding closely related selected individuals.
Assuming inherited defects are caused by pathogens.
Put it right: They result from harmful alleles passed from parents to offspring.
Exam tips
- Use the term ‘inbreeding’ and link it to reduced genetic variation.
- Explain the mechanism by referring to harmful recessive alleles being inherited from both parents.
- Give a named example, such as inherited breathing problems in some dog breeds, to support the explanation.
Try the lesson
The start of the Selective breeding: Selective breeding can lead to ‘inbreeding’ where some breeds are particularly prone to disease or inherited defects. lesson, made from checked teaching notes for this specification point.
Have a go first
What is the name for breeding closely related organisms together, which can make a breed more prone to disease?
Listen
Repeatedly breeding together individuals that show the same desired characteristic reduces genetic variation in the population. If closely related individuals are bred, the population becomes inbred. Inbreeding increases the chance that harmful recessive alleles are inherited from both parents, so offspring may show inherited defects. It also reduces the ability of the population to adapt to new diseases or environmental changes, so some breeds become particularly prone to disease. Examples include certain dog breeds with inherited breathing or joint problems and some crop varieties that are vulnerable to a new pathogen. Breeders may reduce the risk by introducing unrelated individuals to restore variation. A strong answer earns marks for these points. Selective breeding can reduce genetic variation within a breed or variety. Inbreeding occurs when closely related individuals are bred together. Inbreeding increases the chance of offspring inheriting harmful recessive alleles from both parents. Inbred breeds may be particularly prone to disease or inherited defects. A common slip: Thinking that selective breeding always improves health. Instead, it can increase the risk of inherited defects. Exam tip: Use the term ‘inbreeding’ and link it to reduced genetic variation.
Key words
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Inbreeding
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Harmful recessive alleles
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Inherited defects
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Susceptibility to disease
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See every definition
- Inbreeding
- Breeding together closely related individuals, which increases the chance that harmful recessive alleles are inherited from both parents.
- Harmful recessive alleles
- Alleles that, when inherited from both parents, mean offspring may show inherited defects.
- Inherited defects
- Defects that offspring may show when harmful recessive alleles are inherited from both parents.
- Susceptibility to disease
- Being particularly prone to disease, which can occur in some breeds because reduced genetic variation makes a population less able to adapt to new diseases.
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