Lec 14-2 Flashcards
Dominance results from
an allelic interaction
Lethal alleles
Alleles that cause death at early stage development
Changes phenotypic ratio
Dominance relationships and phenotypic ratios
slide 8
Dominance can mean
Normal vs broken protein function
Two traits existing simultaneously
Co-dominance
MN gene locus
Two alleles that control which antigen is expressed on surface of red blood cells
LM encodes M antigen
LN encodes N antigen
Both are expressed when both are present
ABO blood types is an example of
Co-dominance and complete dominance
B and A > i(O)
B = A
Epistasis
One gene masks the effect of another gene at another locus (dominance is one the same locus so this is different)
Epistatic gene
The gene that does the masking
Hypostatic gene
Gene being masked
Epistatic genes may be
Recessive or dominant
Recessive epistasis in labradors
2 genes (B, E):
Gene B – Type of pigment
allele B – black, dominant
allele b – brown, recessive
Gene E – Deposition of pigment in
hair shaft
allele E – Correct deposition,
dominant
allele e – No pigment deposition,
recessive
If ee is present, it will mask B and b, leading to no pigment
Upstream gene
Epistatic to downstream gene
Downstream gene
Hypostatic gene
In recessive epistasis
Two recessive alleles of the epistatic upstream gene are needed to mask
In dominant epistasis
Only one allele is required for upstream gene for masking effect
The color of dog coats is strongly affected by
4 loci in the genome
4 loci in the genome
Agouti
Black
Extension
Spotting
Agouti
Determines depth and distribution of color in coat
5 alleles
Black
Determines whether black is made at all
2 alleles
Extension
Determines where Agouti locus alleles are expressed across the entire coat
4 alleles
Spotting
Locus determines if white spots are present
4 alleles
A(s) means
dogs
Solid black pigments
S means
dogs
No spots
Labrador example
A(s)A(s)
SS
Other locus vary
Leads to solid black with no spots
Dalmatian example
A(s)A(s)
s(w) (Extreme white)
EE (Locus is expressed throughout
Black locus varies throughout (can be black or brown spots)
