Gene Action Flashcards
Non additive Gene action
Qualitative traits
Few genes involves
Gene Action
How the genotype of a particular trait affects the expression in phenotype
Complete dominance
One allele of a pair can mask the expression of the other
RR - red
Rr - red
rr - white
Incomplete dominance
An intermediate phenotype is expressed
RR - red
Rr - roan
rr - white
Epistasis
The phenotypic effect of genes at one locus is dependent upon what alleles are present at another locus district from the first locus
[One gene determines if another gene is expressed]
Complete dominance epistasis
Alleles at one locus control the alleles at another locus
WW or Ww - white wool
ww - allows pigmentation of another allele to be expressed
Recessive epistatis
B_ = Black
bb = brown
C_ = melanin (coloration)
cc = no melanin (albino)
C_ needed for B_ or bb to be expressed (cc blocks the ‘b’ alleles from being expressed)
No Dominance (incomplete dominance)
EX: One allele controls color
The next allele determines the pigment strength
B_ = bay
bb = chestnut
CC = color
Cc = diluter
cc = no color
Sex linkage
Sex determined by inheritance of entire chromosome
Traits controlled by locus on X chromosome
Recessive sex linked
unaffected parents produce offspring that are affected by recessive allele (ex: colorblindness)
Sex influenced
Inheritance of a trait appears to be different in 2 sexes even when they have same genotype
(H = horned in bulls, H = polled in cows)
Sex limited
Expression of trait occurs in only one sex
EX: milk/egg production
(Males carry genes for trait, but don’t express the trait)
Pleitropy
One gene affects more than one trait
Genetic correlation between two traits
Variable expressivity
the existence of more than one grade of a trait
Overdominance
Interactions between gene alleles resulting in a heterozygous superior to either homozygote for that trait
[Extreme heterozygote]
Ex: Sickle cell anemia and malaria
