Genetic diversity Revision Notes

Genetic diversity, genetic bottlenecks, the founder effect, selectve breeding.

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  • Created on: 13-09-13 21:08
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Biology Unit 2- Genetic Diversity
Genetic diversity is greatest between species (interspecific).
Important within species in order to produce variation (intraspecific).
Variation is important as it allows some members of the species to survive if the environment changes (natural
selection).
Mutation is the basis of genetic variation, producing new alleles.
Genetic Bottlenecks
Reduction in the size of the population reduces numbers but also genetic diversity.
Population numbers will increase, but genetic diversity still remains low.
Any changes in environment or new diseases can wipe out the whole population because there is such a lack of diversity.
Example- Cheetahs
Genetic diversity between individual cheetahs is so low that any cheetah can accept skin grafts from any other.
This is the result of a genetic bottleneck about 10,000 years ago.
The Founder Effect
A small group of individuals colonise an area and are successful.
The population increases but genetic diversity remains low.
This leaves the population at risk of becoming endangered because a change in the environment will affect the whole
population.
Example- Africana People
A group of people of Dutch origin who colonised part of South Africa.
They have a very high frequency of the allele for Huntington's disorder.
Human Evolution
Genetic diversity of humans is highest in Africa, which is strong evidence that Homo sapiens evolved in Africa.
Selective Breeding
Used to produce all our crop plants and animal breeds.
Individuals with desirable characteristics are bred together
The offspring with required allele combinations are selected.
Benefits
Bigger yield and therefore food supply.
Increases disease resistance less use of antibiotics.
Increased tolerance to bad conditions e.g. drought.
Farmers in semi-arid areas can grow crops more easily.
Problems
Lack of genetic diversity.
Population at risk from environmental change e.g. new diseases.
Limited gene pool (allele diversity) to produce new breeds.
This is why it is important to maintain rare breeds and wild/ ancestral plant types.
Animal welfare- some cows produce so much milk they get muscle wastage.

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