- Proteins make organisms different. DNA codes for proteins, so therefore, DNA determines variation.
- Alleles determine the characteristics of a gene.
- Genetic diversity is reduced when a species has fewer different alleles.
- Also known as artificial selection.
- Involves identifying individuals with the desired characteristics and using them to parent the next generation. Alleles for unwanted characteristics are bred out of the population.
- The variety of alleles is restricted to a small number of desired alleles. This leads to a population all of which possess the desired qualities, but which has reduced genetic diversity.
- Plants such as wheat, the features selected for include large grains with a high gluten content, short stems and resistance to disease.
1 of 2
Genetic diversity (2)
The founder effect:
- When a few individuals from a population colonise a new region. These few individuals carry with them only a fraction of the alleles of the population as a whole - these alleles may not be representative of the larger population.
- The new population will therefore have less genetic diversity.
- This is often seen when new volcanic islands rise out of the sea.
- Fewer alleles means the population is less able to adapt to changing conditions.
- When some populations of a species suffer a dramatic drop in numbers. Sometimes the reason for this is a chance event, eg volcanic eruption.
- The few survivors will possess a much smaller variety of alleles than the original population.
- As the individuals breed and become re-established, the genetic diversity will remain restricted.
2 of 2