B3. Genetic Diversity Flashcards
What is an allele?
What is genetic diversity?
Why is it important?
What is it increased by? (2 things)
What does it allow to happen?
Remember, there can be different versions of a single gene - these are called alleles. Alleles code for different versions of characteristics
Genetic diversity is the number of different alleles of genes in a species or population. A large number of different alleles in a population means a large variety of different characteristics (e.g. blonde, brown, red or black hair) and a high genetic diversity.
Genetic diversity is important- if a population has low genetic diversity, it might not be able to adapt to a change in the environment and the whole population could be wiped out by a single event (e.g. a disease).
Genetic diversity within a population is increased by:
- Mutations in the DNA forming new alleles. Some of these can be advantageous, whilst others lead to problems
- Different alleles being introduced into a population when individuals from another population migrate into it and reproduce. This is known as gene flow.
Genetic diversity is what allows natural selection to occur because some characteristics are more advantageous than others.
Genetic bottlenecks
What is it?
What does it do?
What happens after it?
A genetic bottleneck is an event that causes a big reduction in a population, e.g. when a large number of organisms within a population die before reproducing. This reduces the number of different alleles in the gene pool and so reduces genetic diversity. The survivors reproduce and a larger population is created from a few individuals
Tip: The gene pool is …
Tip: The gene pool is the complete range of alleles in a population.
The founder effect
What is it?
What is its effect and what can it lead to?
What can it be caused by?
The founder effect describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool
The frequency of each allele in the new colony might be very different to the frequency of those alleles in the original population-for example, an allele that was rare in the original population might be more common in the new colony. This may lead to a higher incidence of genetic disease.
The founder effect can occur as a result of migration leading to geographical separation or if a new colony is separated from the original population for another reason, such as religion.
