Population genetics Flashcards
Discontinous variation
Distinct categories, qualitative, controlled by a few genes
Continuous variation
No distinct categories, quantitative, controlled by lot of genes
What are 3 different types of polygenic trait
Metric: continuous scale
Meristic: discrete scale
Threshold: present or absent
Metric traits
Mean - centre of the phenotypic distribution
Population variance - average squared deviation from the mean
Why is quantitative genetics important
Medicine:
Susceptibility to disease
Complex disorders caused by multiple genetic and environmental factors
Understanding genetic vs environmental causes
Agriculture:
Economically important traits = quantitative traits.
Quantitative genetics theory and the basis for selective breeding programmes
Environmental variation reduces efficiency of selection
Conservation
Conservation of:
endangered species
captive breeding programmes
Consequences of inbreeding and outcrossing.
Whats the equation for phenotype?
Genotype + environment
Vg + Ve + Vge
Vg = Va + Vd Vi
Genetic variance
contribution to phenotypic variation due to set of alleles present in a population and their interactions
Environmental variance
contribution to phenotypic variation caused by differences in environmental conditions (E for environment)
Broad sense heritability
It tells you how much is related to genetics and how much to the environment
Narrow sense heritability
It tells you how much is additive and how much is environmental…
What is h2
h2 estimates vary substantially across traits, environments and different populations
h2 can be used to predict change in the population mean under selection (either natural or artificial)
When h2 increases, the response to selection increases
What does equilibrium mean?
No evolution
Evolution
A change in the frequency of an allele within a gene pool
Hardy Weinberg equilibrium assumptions
Population size is large so no genetic drift - all freq change due to chance as a results of sampling error
No migration/gene flow - changes genetic variation
No mutation or selection
