Color Coat Genetics Flashcards
What are the 2 basic pigments?
Eumelanin and pheomelanin
What is the main protein that eumelanin and pheomelanin derived from?
Tyrosine in melanocytes
What steps does tyrosinase take to convert Tyrosine into the 2 main pigments?
Tyrosine is converted into 3,4 dihydroxyphenylalanine (dopa), then dopaquinone, then eumelanin OR pheomelanin
At the C locus, what is C the allele for in dogs and cats?
Full color
At the C locus, what is the c^ch allele?
chinchilla
How does the chinchilla allele (c^ch) affect coat color?
It reduces pheomelanin, so that tan becomes cream.
What are the alleles at the C locus in dogs?
C, c^ch, c^e, c
What does c^e code for?
white with dark eyes and a dark nose (aka. Samoyed)
What does the c allele code for in both dogs and cats?
true albino- no pigment whatsoever
What are the alleles at the C locus in cats?
C, c^b, c^s, c
The c^b allele encodes what color trait?
brown (i.e. Burmese)
What does the c^s allele encode?
thremolabile melanogenesis (seen in Siamese)
The C locus is responsible for encoding what enzyme?
Tyrosinase
What do the Extension Series and the Agouti series affect the function of?
They affect the function of the melanocyte-stimulating hormone receptor (MSHR)
What is MSHR?
a 7-transmembrane domain, G-protein coupled receptor
alpha-MSH binds to MSHR and stimulates it to make what pigment?
eumelanin
What does the E locus code for?
a receptor, specifically MCR1 (also known as
What are the alleles at the E locus?
E^m, E, e
What are the alleles at the E locus in cats?
E and e
What does E^m code for in dogs?
Black Mask (Pug)
What does E code for in dogs?
it restricts pheomelanin production (so that the coat will be dark throughout because eumelanin takes over)
What does e code for in dogs?
extension of pheomelanin in the entire coat with a dark nose, eyes, and footpads
What does the E code for in cats?
E is full color
What does the e code for in cats?
“amber” only seen in Norwegian Forrest Cat. It affects the hue of the yellow seen
What locus is identified as the paracrine-signaling molecule?
the Agouti Locus
How does the agouti peptide from the A locus interact with MCR1 produced by the E Locus?
It is a paracrine signaling molecule that inhibits the binding of melanocortins to MCR1. (It’s an antagonist gene to the MCR1 made by the E locus)
What are the alleles for the A locus in a dog?
a^y, a^w, a^t, a,
What does a^y code for?
tan, sable, red (pheomelanin), this is the dominant allele because when it is on, it always inhibiting the MCR1.
What does a^w code for?
agouti (alternating dark and light bands on hairs)
what does a^t code for?
dark trunk, tan extremities (Doberman pinscher)
What does a code for?
recessive black (full color)- the agouti peptide is inhibited
What are the a alleles at the A locus in the cat?
A and a
What do the A and a alleles code for?
A= agouti a= non-agouti (full- color)
The agouti peptide must be expressed to have a tabby cat. True/ False?
False: the agouti peptide is NOT necessary for the expression of tabby in cats
What is the K locus?
the Dominant Black locus- it encodes for CBD103
What is CBD103?
A beta-defensing
How does action does CBD103 have?
it interacts with agouti peptide and prevents it from binding to MCR1
What are the alleles at the K locus? (**this is only in a dog)
K^B, k^br, k^y
Which allele codes for brindle?
k^br
Which allele codes for solid black, brown, or blue?
K^B- this is eumelanin pigmentation only
What does the k^y allele code for?
expression of agouti alleles that will express pheomelanin– this allele allows for the expression of yellow
What is the mechanism behind the brindle phenotype?
it is epigenetically controlled
What is the B locus and what does it code for?
the Black/Brown series and it codes for a Tyrosine related protein (TRP1)
Name the three mutations the B locus has in it.
1) a stop codon at exon 5 (nonsense mutaton)
2) a deleted proline at exon 5 (deletion)
3) Ser to Cys at amino acid 41 (missense mutation)
What are the 2 alleles at the B locus in a dog and what do they code for?
1) B for black
2) b for chocolate (and chocolate nose, footpads, iris)
What are the 3 alleles at the B locus in a cat?
B, b, and b^e
What does the B allele code for in cats?
black
What does the b^e allele code for in cats?
red (seen in Abbyssianian)
What does the b allele code for in cats?
chocolate (Havana Brown)
