BRAINCAKEGene Pools
Revision notes for Gene Pools in Edexcel Biology (9BI0). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Population GeneticsPopulation genetics is the study of the genetic make-up of populations and how it changes over time.
- Allele FrequencyThe allele frequency is the proportion of all the alleles of a gene in a population that are a particular allele.
- Hardy Weinberg EquilibriumThe Hardy-Weinberg principle (proposed in 1908 by G.
- Hardy Weinberg EquationThe Hardy-Weinberg equations link allele frequencies to genotype frequencies in a population in equilibrium.
- Conditions of the Hardy Weinberg EquilibriumThe Hardy-Weinberg principle only predicts constant allele frequencies if certain conditions are met.
- MutationsA mutation is a change in the base sequence of DNA.
- Non-Random MatingThe Hardy-Weinberg principle assumes random mating: every individual is equally likely to mate with any individual of the opposite sex, whatever its…
- Different Sized PopulationsThe Hardy-Weinberg principle assumes a very large population.
- IsolationThe Hardy-Weinberg principle assumes that there is no migration: no individuals, and so no alleles, move into or out of the population.
- Selection PressureA selection pressure is any environmental factor that affects the chance of an organism surviving and reproducing.
- Population BottlenecksA population bottleneck is a large, sudden reduction in the size of a population, caused by an event such as a natural disaster, disease, habitat…
- The Founder EffectThe founder effect happens when a small group of individuals leaves a large population and starts a new population somewhere else, for example by…
- Stabilising SelectionStabilising selection is natural selection that favours individuals with phenotypes close to the mean and selects against both extremes.
- Directional SelectionDirectional selection is natural selection that favours individuals with a phenotype at one extreme of the range.
- Disruptive SelectionDisruptive selection is natural selection that favours individuals at both extremes of the range and selects against individuals with intermediate…
- Genetic DriftGenetic drift is a change in allele frequencies in a population from one generation to the next that happens by chance, not because an allele gives…