Chapter 20 - Patterns of Inheritance and Variation Flashcards
What is the Hardy-Weinberg principle?
In a stable, non-evolving population, allele frequencies stay constant
What assumptions are made in the Hardy-Weinberg principle?
- Large population size
- Random mating
- No mutations
- No selection pressure so no evolution
- No gene flow
In the Hardy-Weinberg principle, what letter are dominant alleles represented by?
p
In the Hardy-Weinberg principle, what letter are recessive alleles represented by?
q
What is the equation for the Hardy-Weinberg principle?
p^2 + 2pq + q^2 = 1
What does p + q always equal in the Hardy-Weinberg principle?
p + q = 1
You can use this to work out what p or q is when you are given only one of the values
What is the gene pool?
The sum total of all the genes in a population
What is allele frequency?
The relative frequency of a particular allele in a population
In what situations would the Hardy-Weinberg principle not apply?
In any population in which any one of the assumptions of the Hardy-Weinberg principle are not met e.g. small population, gene flow occurring
What different factors affect evolution?
Mutation
Changes in population size
Genetic drift
Selection of favourable alleles
How does mutation affect evolution?
Mutation leads to genetic variation, in which favourable alleles can be selected
What are the two different types of factors affecting population size?
- Density dependent factors
- Density independent factors
What are density dependent factors?
Factors dependent on population size e.g. competition, predation
What are density independent factors?
Factors independent of population size e.g. climate change, natural disaster
What are small changes in population often caused by and what do they lead to?
They are often caused by migration, and can lead to gene flow
