quantitative genetics - lecture 16 Flashcards
What are the components of phenotypic variation?
Vp = Vg + Ve + Vge
What are the components of genetic variation?
Additive genetic variance ( heritable) + Dominance ( non - inheritable) +gene interaction ( non - inheritable)
what are the two types of heritability?
Broad sense and Narrow sense
definition of broad sense heritability
The proportion of phenotypic variation attributable to genetic differences between individuals
broad sense formula
H^2 = Genetic variance/ Phenotypic variance
Narrow sense formula
h^2= Additive genetic variance/phenotypic variance
Phenotypic correlation
When points represent different individuals
Genotypic correlation
When points represent different genotypes
Pleiotropy
When a single gene affects multiple characteristics/ traits
What is Linkage disequilibirum?
Linkage disequilibirm occurs when there is an association between alleles at different loci ( e.g allele A tends to be found with B)
coupling gamates vs replusion gametes
coupling - similiar traits together
repulsion - dissimilar traits together
What happens if there is an overrepresentation of coupling and repulsion gametes?
Then there is a linkage disequilibrium
what dos coupling do?
A and B are more likely to be inherited, therefore there is correlation between height and foot size
Why is linkage disequilibirum an unlikely explanation for most genetic correlations?
recombination removes linkage disequilibirum
What happens when recobination occurs ni an individual that is heterozygous at only one locus( single heterozygote)?
No new haplotypes are produced
What happens when recombination occurs in a double heterozygote?
New haplotypes are produced
How do you find the genetic basis to variation?
- Mapping quantitative trait loci
- Genome - wide studies
Whatt is a QTL?
A Quantitative Trait Locus (QTL) is a location in the genome that causes different values of the trait in question
Does not have to be a gene
What are QTL’s associated in the genome?
Not Associated with differences in proteins , but rather , differences in gene expression
How to do QTL anaylsis?
- Test whether different genotypes have different trait values
- done using gnetic markers
- Identify casual variation linked to thse markers
What is the prupose of QTL?
Quantitative trait locus (QTL) analysis is a statistical method that links two types of information—phenotypic data (trait measurements) and genotypic data (usually molecular markers)—in an attempt to explain the genetic basis of variation in complex traits
What is Genome Wide Association study ?
Identifies casula loci by testing whether groups with different phenotypes have different frequencies of alleles at a locus
what does vG stand for?
Genetic variation
What does Ve stand for?
Environmental variation
What does Veg stand for?
Genotype - environmental variation
What is the formula for genetic variation
?
Va + Vd + Vi
What does Va stand for?
Additive genetic variance
What does Vd stand for?
Dominance genetic variance
What does Vi stand for?
Gene interaction variance
Definition of narrow sense heritability
theproportionof phenotypic variation that contributes to the resemblance between parents and offspring
