Complex Traits Flashcards
What are complex traits?
The phenotypic variation that arises from a combination of genes
What is the difference between complex & simple traits?
Monogenic traits–>1 major gene that contributes to the Phenotype
Polygenic traits–> Several loci
How is stature considered a polygenic trait?
-influenced by 80-90% genetic variation
-single nucleotide change in the HMGA2 gene
-20 loci that influence adult height
Polygenic vs pleiotropy
polygenic–> many genes contribute to a single effect
pleiotropy–> A gene has multiple effect
The formula for variation between people is due to
genetic differences between them and how much is due to them experiencing different environments
Variance(phenotype) = Variance(genetics) + Variance(environment)
Heritability formula
H = VarG / VarP = VG / VP
= VG/VG + VE
What is H in the heritability formula?
The proportion of the phenotypic variation in a population that is attributable to genetic variation among individuals
What does this graph show?
The closer to one means that the impact of genetic variation is higher on the phenotype Vg.
Measuring heritability
H= correlation between relatives(eg. height)/coefficient of relationship(0.5 between parent & child)
Complications of heritability
-H is not constant, varying in space & time
-Assortative mating overestimates H
-shared environment can overestimate H
-Genotype-Environment interaction
Identify the model and explain what is demonstrates
Polygenic Inheritance model, each gene has a small effect which cannot be identified by observing the phenotype
How does assortative mating affect genotype frequency
-lead to an overestimate of H
-can cause deleterious biological consequences, increasing homozygote
Coefficient of inbreeding(F)
-probability an individual has 2 genes at a locus that are identical by descent
F = 1/2 (r) of parents, r is the coefficient of parent
How is the r value calculated?
r=(1/2)^steps btw the pair
How is the r value calculated?
r=(1/2)^steps btw the pair
