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Equine Science ANBI 320 > Colour Genetics > Flashcards

Colour Genetics Flashcards

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1
Q

why study colour

A
  • to determine the association of different traits and genes affect other body functions, not just colour
  • melanogenesis genes impact additional biological systems
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2
Q

what is eumelanin

A

black and brown colours

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3
Q

what is phaeomelanin

A

yellow and red colours

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4
Q

what is melanin

A
  • produced by melanosomes
  • found in melanocytes
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5
Q

what causes different pigments

A
  • melanin granule modifiers = the size of the granules and their ability to reflect light
  • arrangement in follicles
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6
Q

what are the two base colours

A
  • black/bay
  • red
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7
Q

what causes black

A

-agouti (ASIP)
- homozygous recessie a/a causes black

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8
Q

what causes bay

A
  • agouti (ASIP)
  • heterzygous dominant
  • A/ dominante for bay
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9
Q

what causes brown

A
  • no evidence for brown
  • one additional gene for brown that is recessive
    = another gene at agouti causing a different variation of black
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10
Q

what causes chestnut

A
  • MC1R
  • e/e homozygous recessive
  • no eumelonine, epistativ to agoutie
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11
Q

what casues a dark chestnut

A
  • E/
  • heterozygous dominant turning it into a dark bay chestnut
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12
Q

why do red heads need more anasthetics

A
  • MC1R transcripts
    -in immune system, in preiacquiductal grey (PAG) matter of the brain
  • contain opioid receptors
    PAG- pain modulation
    e/e will lower analgesic effects
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13
Q

what colours are modified by dilution

A
  • cream
  • pearl
  • sunshine
  • mushroom
  • dun
  • silver
  • champagne
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14
Q

what causes cream

A
  • mutation in melanocyte transporter protein gene MATP (SLC45A2)
  • transports molecules required for melanosome function
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15
Q

what is cream

A
  • Cr, incomplete dominance over chestnut and bay
  • heterozygous genotype
  • mutation in melanocyte transporter protein gene MATP
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16
Q

what can cream be expressed by

A
  • buckskin
  • palomino
  • cremello
  • perlino
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17
Q

what causes smokey black

A
  • a/a E/- Cr/cr
  • heterozygous
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18
Q

what causes smokey cream (peeling)

A

a/a E/- Cr/Cr
- homozygous

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19
Q

what causes a buckskin

A
  • heterozygous - bay into buckskin
  • A/ E/ Cr/cr
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20
Q

what causes perlino

A
  • homozygous bay
  • A/ E/ CR/CR
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21
Q

what casues palomino

A
  • recessive e/e
  • heterozygous on chestnut
  • e/e Cr/cr
    seen in mane and tail
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22
Q

what causes cremello

A

homozygous on chestnut
- e/e CR/CR
- distinguished through lineage or DNA testing

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23
Q

what casues pearl, sunshine and snowdrop

A
  • recessive mutations in MATP
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24
Q

what is pearl

A
  • recessive pearl (prl) dilustion mutation affects eumelanin and phaeolmelanin
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25
Q

what causes black pearl

A
  • homozygous recessive (mutation)
  • a/a E/ prl/prl
  • seem generally in quater or iberian horses
26
Q

what casues bay pearl

A
  • A/ E/ prl/prl
  • homozygous recessive
  • more extreme dilution
27
Q

what causes a chestnut pearl

A
  • e/e prl/prl
28
Q
A
29
Q

what causes sunshine

A
  • believed to behaved like prl
  • no homozygous identified
  • mutation identified in conjunction with CR
  • e/e CR/sun
30
Q

what casues snowdrop

A
  • usually gypsie vanour
  • recessive mutation
  • dilutes eumelanin and phaeomelanin
  • phenotype similar to CR/CR
    close to cream BUT has colour spots
  • sno/sno
31
Q

what causes mushrooms

A
  • recessive mutation in MFSD12
  • identified in shetland ponies
  • gene responsible for the production of both eumelonin, phaeomelonin
  • e/e MU/ mushroom
  • e/e mu/mu mushroom chestnut
  • A/ E/ mu/mu mushroom on bay
32
Q

what causes DUN

A
  • thought to be a wild type/ original colour of the horse
  • Dun D - dominant
  • mutation in TBX3, regulates distribution of pigment in hair follicles
  • dorsal and leg stripes
33
Q

what colours blue/black dun and Grullo

A
  • a/a E/ D/
  • characterized by back stripe and leg stripes
34
Q

what causes yellow (bay) dun

A
  • A/ E/ D/
  • dun on bay
  • black hair and tail, back stripe and stripes on legs
35
Q

what causes red dun

A

e/e D/
- some dilution of coat colours and stripe with leg stripes

36
Q

what causes silver

A
  • silver dilution mutation (z) is dominant if base colour is black or bay; no effect on chestnut
37
Q

what causes silver dapple

A
  • a/a E/ Z/
  • largly seen in mane and tail
  • silver on black
38
Q

what causes red silver dapple

A
  • A/ E/ Z/
  • silver on bay
39
Q

what causes icelandic horse

A
  • e/e Z/
  • chestnut
40
Q

what is the pleiotropic effect

A
  • effects colour + eyes effects more then 1 trail
  • incomplete dominant causing
  • horses with the silver gene heterozygous have eye problems (cysts)
  • homozygous - suffers with lots of things in the eyes
41
Q

what causes champagne

A
  • champange (CH) allele is dominant to non-champagne allele ch
  • mutation in SLC36A1
  • coloured hairs on pink skin
  • champagne (CH) dilutes eumelanin and phaeomeltnin
42
Q

what causes champagne black

A
  • a/a E/ CH/
43
Q

what causes amber champagne

A
  • A/ E/ CH/
44
Q

what causes gold champagne

A
  • e/e CH/
  • coloured hair on pink skin
45
Q

what is roan grey

A
  • intersperse coloured hair
  • added in white hairs
46
Q

what causes progressive whitening

A
  • a/a E/ G/ - white on black
  • A/ E/ G/ - white on bay
47
Q

what causes roan chestnut

A
  • e/e G/
  • progressive whitening
48
Q

what is common with grey horses

A
  • melanomas
  • 85% of all horses will have them
  • melanomas by 15 or younger, they are often beniegh bu can turn terminal or be in areas that will bother the horses
49
Q

what are the grey rankings for melanomas

A
  1. grey on black
  2. grey on bay
  3. grey on chestnut (homozygous)
  4. grey on chestnut ( heterozygous)
50
Q

what causes black(blue) Roan

A
  • a/a E/ RN/rn
51
Q

what causes bay (red) roan

A

A/ E/ Rn/rn
- scars and scrapes will return fully pigmented

52
Q

what causes strawberry roan

A
  • e/e RN/rn
  • they appear lighter becasue of hair is into mingled
53
Q

what are the different depigmentations

A
  • dominant white
  • tobiano
  • overo
  • splashed white
  • sabino
54
Q

what causes dominant white

A
  • 34 mutations identified in KIT
    W/w
  • variable depigmentation 50-100% of skin and hair
  • ovverides all other colour genes
55
Q

what causes spotting tobiano

A
  • To/
  • colour spotting ( variable expressivity )
  • on grey it will eventually turn them white
  • 20-80% depigmentation
56
Q

what causes overo

A
  • dominant 1 copy
  • recessive lethal
  • paint looking
  • associated with deafness - a loose association is blue eyes and white ears = deaf
57
Q

what causes splashed white

A
  • SPL/
  • associated with deafness
  • phenotypic overlap with overo
58
Q

what causes sabino

A
  • mutation identified
  • phenotypic overlap with overo
  • belly spot/ chine white
  • socks are irregular and pointed at the top
  • common in clidstales
  • dominant allele
  • no negative effects identified
59
Q

what colours lead to death

A
  • RN/RN
  • W/W
  • O/O
60
Q

what is N+

A
  • postulation
  • no white markings/ dominant to Nn
  • may modify expressions of tabiano, Sabino, over, and splashed white
61
Q

what causes leppard spotting

A

Lp/Lp = few spots
Lp/lp = leopard
lp/lp = solid
- sex influenced = males are more likely to have more white

  • dominante PATN1 allele affects amount of white

Equine Science ANBI 320 (20 decks)

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