ANSC 313 Lecture Notes - Lecture 24: Quantitative Trait Locus, Epistasis, Heritability
LECTURE 2!
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example of selecting "half as hard" on heterozygotes!
breeder would need to be able to identify heterozygotes. !•
in this case, highland breeder wants no white and more dark red cattle, recognizing fewer light •
red should be bred too!
(p would increase)!•
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incomplete dominance w(AA) > w(Aa) > w(aa)!
i.e fitness of the heterozygote is in between the fitness of the homozygotes!•
int this case both heterozygotes.....!•
example: litter size by what genotype this have!•
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selection against heterozygote!
charolais are white because they are homozygotes for a recessive d dilution allele at the RMEL •
gene!
angus are homozygous D/D!•
since q= frequency of the d allele!•
if q>p, d will be fixed, cattle will be white!•
if p>q, D will be fixed, cattle will be dark red or black!•
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Goal of animal breeder : !
Change Phenotype!•
improve environment!◦
change genotype of breeding stock!◦
phenotype= genotype + environment!
Genotype effects!•
additive effects!◦
dominance deviation!◦
interactive effects!◦
Environment effects!•
feeding!◦
housing!◦
stress!◦
health!◦
ideally should select genotype not phenotype!
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polygenic inheritance!
many genes influence one trait !•
when >3 genes = polygenic!•
coat color in cattle!◦
head shape in horses!◦
litter size in cats!◦
herding ability in dogs!◦
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example: Additive effects!
height in dogs!•
HHHHHH= tall!◦
hhhhhh= short!◦
