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ANBI 360 > dog coat colour > Flashcards

dog coat colour Flashcards

1
Q

why coat colour

A

-hallmark traits in most breed standards
-easily observed/recorded (involve breeders in research and students in teaching
-because melanoblasts and neuroblasts derive from the same progenitor cells, there are important development issues

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2
Q

side effects of domestication syndrome

A

-smaller brain size
-shortened snout
-weakened ear cartilage
-tail cartilage shortening/curling
-reduced tooth size

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3
Q

what are melanocytes

A

cells that sit at the base of the hair follicle and give rise to colour

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4
Q

what are the two melanin pigments

A

-phaeomelanin (red, yellow, cream)
-eumelanin (black, brown, grey)

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5
Q

dog coat colour genetics

A

-interactions amongst different loci
-dogs may have a particular genotype at one locus and yet not exhibit the expected phenotype because of an incompatible genotype at another locus

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6
Q

dominant/recessive

A

-dominant is black which is phenotypically displayed if present
-recessive is red and is phenotypically displayed if in the homozygous state

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7
Q

co dominant traits

A

heterozygote has different phenotypes

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8
Q

dominance hierarchy

A

one mutation has stonger effects then another

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9
Q

compound heterozygotes

A

two different mutant alleles at a
particular gene locus, one on
each chromosome

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10
Q

epistasis

A

alleles at one locus mask
expression of alleles at another
locus

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11
Q

E Locus = Extension locus
(MC1R)

A

▪ Melanocortin Receptor 1 (MC1R)
▪ Melanocyte stimulating hormone (MSH)
▪ EM > EG > E > (ea)>e

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12
Q

What is the role of MC1R?

A

MC1R gene provides instructions for making a protein called the melanocortin 1 receptor. This receptor plays an important role in normal pigmentation. The receptor is primarily located on the surface of melanocytes, which are specialized cells that produce a pigment called melanin.

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13
Q

e Allele at MC1R

A

-317 amino acids long
-* “E” allows both eumelanin and phaeomelanin to be
produced
* Mutation in DNA at position 914 C>T results in protein
termination at amino acid 306 (p.R306ter)
* “e” causes “clear red” because the receptor has a
premature stop codon

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14
Q

e/e genotype

A

Dogs that are e/e do not have a single black or brown hair
on them!
They are “clear red”.
e/e is epistatic (masks) other alleles at A (Agouti) and K
(beta defensin)

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15
Q

EM Allele of MC1R

A

Melanistic Mask (frencie)
Why the face & ears? Highest
concentration of pigment/neural
cells
* Not visible on solid black dogs or
dogs with a white mask
EM Allele of MC1R

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16
Q

Grizzle EG

A

▪ In two “old” breeds, Saluki and Afghan
Hounds, a pattern exists that does not
occur in other breeds
▪ The pattern includes a grizzled dorsal
surface

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17
Q

Grizzle in sluki and afgan

A

▪ facial marking is considered a hallmark of this pattern
Grizzle (Saluki)- E locus: EG/_
A locus: atat
Domino (Afghan)- E locus: EG
A locus: atat
Black-and-tan (saluki)- E locus: E/_
A locus: atat
Black-and-tan (afghan)- E locus: E/_
A locus: atat

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18
Q

Northern Domino (eA)

A

▪ R301C mutations in MC1R has been observed in different
dog breeds, but with unknown consequence
▪ This mutation found in archeological dog specimens over
10,000 years old not found in any wolf samples or “wolf-
like” ancient specimens (Anderson et al 2020)
▪ Found in 1.5% of dogs genotyped (12,000 dogs sampled)
and all Alaskan Malamute dogs tested
▪ Not in the Asian Spitzes (e.g. Shiba Inu, Akita)

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19
Q

A locus = ASIP

A
  • Agouti Signalling
    Protein
  • Multiple Alleles
  • Dominance Hierarchy
    ay > aw > at > a
  • New mutations found
    recently
  • Dreger et al 2020
  • Banasch et al 2021
    -eumelanin and pheomelanin found in the same hair (alternating)
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20
Q

ASIP - aw

A
  • Banded/Sable (aw) is the “wild type”
  • Occurs in wolves and coyotes - the “wild” standard
  • “fixed”
    banded hairs on
    most of the dorsal
    surface
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21
Q

ASIP - ay

A

▪ Fawn or sable (note nomenclature is
inconsistent among breeds)
▪ “mostly reddish”, but some hairs can be
black
▪ Some red hairs can have black tips
-also shaded sables

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22
Q

ASIP - at

A

▪ Black-and-tan, black with tan points, or tricolor
▪ at is caused by a promoter mutation in ASIP

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23
Q

ASIP- a

A

-recessive black (a) is cause by a premature stop codon
-rare mutation
-all black german shepherd dogs and shelties and gronendaels
-som herding breeds

24
Q

saddle tan

A

-saddle tan and black and tan both give genotype atat at agouti signalling protein (ASIP)
-what is the additional gene or mutation for saddle tan?
-saddle tan is a modification of black and tan to get saddle tan the animal must be black and tan atat and agouti locus
-the dominant allele at RALY causes saddle tan

25
Q

what genotypes give you grizzle

A

EG/EG; EG/E; EG/e

26
Q

what is a melanistic mask

A

EM/_

27
Q

what is the phenotype of e/e

A

clear red ie. Irish setter

28
Q

what is the wild type of ASIP

A

aw

29
Q

what is the dominant of ASIP

A

ay sable or fawn

30
Q

what does atat look like

A

black and tan

31
Q

dom hierarchy of ASIP

A

ay, aw, at, a

32
Q

what is a for ASIP

A

responsible for balck dogs in herding breeds

33
Q

K locus

A

-KB, KBr, Ky
-uses beta-defensin 103
-can get eumelanin if you have a working receptor
-KB allele negates expression of phaeomelanin (red) pigment form ASIP

34
Q

black genotypes

A

-there are two that cause SOLID black
-a few breeds can have both genotypes
-most non herding breeds: KB/, E/
-herding breeds: a/a

35
Q

brindle

A

-KBr
-KB, KBr, Ky
-gene causing spacing
-alternating eumelanin and phaemelanin
-light brindling, heavy brinding, reverse brindling

36
Q

B locus

A

-TYRP1
-3 mutations causing brown bc, bd, and bs
-4th mutation found in 2018
-S41C, Try185ter, Q331er, 345delP

37
Q

B locus and skin

A

-all have brown nose and pads
-if not brown they’d be black
-doesn’t affect pheomelinin

38
Q

cocoa colouring

A

-in franchies
-its not black its just a really dark brown
-HPS Co/Co TYRP b/b

39
Q

MC1R + TYRP1

A

-“red” dogs e/e homozygous for TYP1 mutations b/b have brown noses and pads
-“red” dogs e/e with wild type TYRP1 allele (B) have black noses and pads

40
Q

D Locus

A

-melanophilin (MLPH)
-grey or blue colour recessive (dd)
-mutation found in MLPH gene
-three mutations currently identified
-d1 (more common)
-d2 (sloughi, chow chow, and thai ridgeback)
-d3 (rare)
-affects both eumelanin pigments black and liver

41
Q

if you have a black dog and it has bb what colour is it

A

brown

42
Q

if you have a black or brown dog with dd what colour are they

A

one is blue and the other is lilac

43
Q

what does the D locus affect

A

both eumelanin pigments black and liver

44
Q

M locus

A

-PMEL or SILV
-premelanosome protein (silver locus)
-MM (deaf) microphthalmia and anophthalmia
-Mm (merle)
-mm not merle

45
Q

merle- PMEL (SILV)

A

-short interspaced nuclear element is inserted in the gene disrupting the function
-thymine (T) nucleotide number varies
-T (54-65) not merle
-T (90-101) + SINE=all merle dogs studied thus far
-harder to see in fawn/sable dogs
-e/e is epistatic to merle

46
Q

harlequin spotting- PSMB7

A

-gene: proteosome beta 7
-one H and M allele required
-H/H is fetal lethal
-unique to great dane
-H/h, M/m
-merle but when not a black spot its white

47
Q

what is white

A

not a colour but the absence of colour

48
Q

what could cause a purebred lab to have white on chest

A

-melanocytes just didn’t reach that area
-can happen if the bitch is sick during pregancy

49
Q

S locus-MITF

A

-melanocyte inducing transcription factor (MITF) of microphthalmia- associated transcription factor
-MITF has been reported to cause spotting in some breeds
-SINE insertion resulting in piebald (sP)
-SS-regular
-SsP-minor white markings
-sPsP-major white markings, amy be deaf

50
Q

irish spotting

A

-Bernese, Australian shepherd
-equal on both sides (symmetrical)
-sisi

51
Q

panda white spotting

A

-german shepherd
-autosomal dominant mutation “P”
-embryonic lethal
-mutation in KIT spotting gene

52
Q

In locus- intensity

A

-in many breeds e/e dogs are cream to white instead of red
-these dogs are “fixed” for a paling genotype or intensity genotype
-mutation found in MFSD12 gene in golden retrievers and yellow labs
-KITLG mutation causes shades of phaeomelanin

53
Q

In locus- intensity cream/ white

A

-samoyeds have been genotyped as e/e and a/a
-the melanocytes can produce pigment
-a allele found only in herding breeds

54
Q

albinism- C locus- SLC45A2

A

-visual acuity comprosed
-albinism in other animals caused by tyrosinase
-SLC45A2 mutations- caz, cal

55
Q

ticking and roan

A

-ticking spots/flecks of colour on white (T)
-roan is mottled white areas
-ticking more on legs and muzzle, while roan is more even over body
-gene not known
-ticking and roan may be alleles of the same gene
-can look like Merle but this is colour coming through white

ANBI 360 (28 decks)

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