Population and Quantitative Genetics Flashcards
(44 cards)
How would you work out genotypic frequency?
- no. of individuals with genotype / total no. of individuals
What is the Hardy Weinberg Model and what are the assumptions of it?
Genotypic/allele frequencies will remain same after single generations of random mating following assumptions:
- large population
- random mating
- no mutations
- no migration or immigration
- no selection
Why is the HWM often wrong?
Non random mating can occur - (3 types)
1) Positive assortative mating - similar individuals mate with similar individuals
2) Neg assortative mating - diff with each other
3) Inbreeding - relatives with each other
What are the issues associated with inbreeding?
- reduced fitness
- increases homozygosity
What are the causes of change in allele frequency?
1) Genetic drift - random changes in allele frequency ( error = 1/2N) - Bottleneck is an example of this: Drastic reduction in pop size, new pop isn’t representative of old one. Founder effects too.
2) Natural Selection - diff genotypes have diff fitness, leads to changes in allele freq as favours certain alleles
3) Migration - movement of alleles from one pop to another. Reduces genetic differences between populations.
What is fitness?
A measure of the average contribution to the next generation
What is overdominance?
Heterozygote has highest fitness, neither allele favoured.
- selection maintains both alleles
What is a meristic (countable) trait?
- determined by multiple genetic and environmental factors and measured in whole numbers eg. animal litter size
What is Threshold traits?
- measured by presence or absence
- e.g susceptibility to disease
Definition of Phenotypic variance
- total amount of variation among individuals in some trait, caused by underlying components of variation.
Definition of Broad sense Heritability
- proportion of phenotypic variation attributable to genetic differences between individuals
- H2 = Vg / Vp
Definition of Narrow sense Heritability
- proportion of phenotypic variation that contributes to the resemblance between parent and offspring (additive genetic variance)
- H2 = AGV / Phenotypic V
- measured by regulation
- linear relationship between parent and offspring
What are the components of Phenotypic variation?
- Genetic Variance ( VG)
- Environmental Variance ( VE)
- Genotypic-environmental interaction variance (VGE)
VP = VG + VE + VGE
What are the components of Genetic variation?
Heritable Variation - additive genetic variance ( VA)
Non heritable variation -
1) Dominance genetic variance (VD)
2) Gene interaction (epistatic) - VI
What is regression?
- predicting the value of one variable if the value of other is given
What is regression coefficient?
- represents the slope of the regression line, indicating how much one value changes on average per increase in the value of another variable.
- flat line = zero heritability
What is linkage disequilibrium?
- 2 loci A and B with alleles A/a and B/b
- and Linkage EQ combos of alleles at A and B should be randomly assorted.
- LINKAGE DISEQ occurs when there’s an association with alleles at diff loci. EG A found with B
- coupling of A and B and a and b
- repulsion of A and b and B and a
What removes linkage diseq?
- recombination
What is pleiotropy?
- traits usually inherited together, a single locus / gene that affects the expression of multiple traits.
What is Quantitative Trait Locis?
- location of the genome that causes diff values of the trait in question
- tests done using genetic markers
What is the genome wide association?
- identifies casual loci by testing whether groups with diff phenotypes have diff frequencies of alleles at locus
- using a dense sequence data but also marker data
What is additive genetic variance?
- predicts resemblance between parents and offspring
What are breeding values?
- twice mean deviation of its progeny from the population mean phenotype
What is biological evolution?
- genetic changes in a group of organisms
