Colour Genetics Flashcards
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
2
Q
what is eumelanin
A
black and brown colours
3
Q
what is phaeomelanin
A
yellow and red colours
4
Q
what is melanin
A
- produced by melanosomes
- found in melanocytes
5
Q
what causes different pigments
A
- melanin granule modifiers = the size of the granules and their ability to reflect light
- arrangement in follicles
6
Q
what are the two base colours
A
- black/bay
- red
7
Q
what causes black
A
-agouti (ASIP)
- homozygous recessie a/a causes black
8
Q
what causes bay
A
- agouti (ASIP)
- heterzygous dominant
- A/ dominante for bay
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
10
Q
what causes chestnut
A
- MC1R
- e/e homozygous recessive
- no eumelonine, epistativ to agoutie
11
Q
what casues a dark chestnut
A
- E/
- heterozygous dominant turning it into a dark bay chestnut
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
13
Q
what colours are modified by dilution
A
- cream
- pearl
- sunshine
- mushroom
- dun
- silver
- champagne
14
Q
what causes cream
A
- mutation in melanocyte transporter protein gene MATP (SLC45A2)
- transports molecules required for melanosome function
15
Q
what is cream
A
- Cr, incomplete dominance over chestnut and bay
- heterozygous genotype
- mutation in melanocyte transporter protein gene MATP
16
Q
what can cream be expressed by
A
- buckskin
- palomino
- cremello
- perlino
17
Q
what causes smokey black
A
- a/a E/- Cr/cr
- heterozygous
18
Q
what causes smokey cream (peeling)
A
a/a E/- Cr/Cr
- homozygous
19
Q
what causes a buckskin
A
- heterozygous - bay into buckskin
- A/ E/ Cr/cr
20
Q
what causes perlino
A
- homozygous bay
- A/ E/ CR/CR
21
Q
what casues palomino
A
- recessive e/e
- heterozygous on chestnut
- e/e Cr/cr
seen in mane and tail
22
Q
what causes cremello
A
homozygous on chestnut
- e/e CR/CR
- distinguished through lineage or DNA testing
23
Q
what casues pearl, sunshine and snowdrop
A
- recessive mutations in MATP
24
Q
what is pearl
A
- recessive pearl (prl) dilustion mutation affects eumelanin and phaeolmelanin
25
what causes black pearl
- homozygous recessive (mutation)
- a/a E/ prl/prl
- seem generally in quater or iberian horses
26
what casues bay pearl
- A/ E/ prl/prl
- homozygous recessive
- more extreme dilution
27
what causes a chestnut pearl
- e/e prl/prl
28
29
what causes sunshine
- believed to behaved like prl
- no homozygous identified
- mutation identified in conjunction with CR
- e/e CR/sun
30
what casues snowdrop
- usually gypsie vanour
- recessive mutation
- dilutes eumelanin and phaeomelanin
- phenotype similar to CR/CR
close to cream BUT has colour spots
- sno/sno
31
what causes mushrooms
- 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
what causes DUN
- 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
what colours blue/black dun and Grullo
- a/a E/ D/
- characterized by back stripe and leg stripes
34
what causes yellow (bay) dun
- A/ E/ D/
- dun on bay
- black hair and tail, back stripe and stripes on legs
35
what causes red dun
e/e D/
- some dilution of coat colours and stripe with leg stripes
36
what causes silver
- silver dilution mutation (z) is dominant if base colour is black or bay; no effect on chestnut
37
what causes silver dapple
- a/a E/ Z/
- largly seen in mane and tail
- silver on black
38
what causes red silver dapple
- A/ E/ Z/
- silver on bay
39
what causes icelandic horse
- e/e Z/
- chestnut
40
what is the pleiotropic effect
- 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
what causes champagne
- 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
what causes champagne black
- a/a E/ CH/
43
what causes amber champagne
- A/ E/ CH/
44
what causes gold champagne
- e/e CH/
- coloured hair on pink skin
45
what is roan grey
- intersperse coloured hair
- added in white hairs
46
what causes progressive whitening
- a/a E/ G/ - white on black
- A/ E/ G/ - white on bay
47
what causes roan chestnut
- e/e G/
- progressive whitening
48
what is common with grey horses
- 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
what are the grey rankings for melanomas
1. grey on black
2. grey on bay
3. grey on chestnut (homozygous)
4. grey on chestnut ( heterozygous)
50
what causes black(blue) Roan
- a/a E/ RN/rn
51
what causes bay (red) roan
A/ E/ Rn/rn
- scars and scrapes will return fully pigmented
52
what causes strawberry roan
- e/e RN/rn
- they appear lighter becasue of hair is into mingled
53
what are the different depigmentations
- dominant white
- tobiano
- overo
- splashed white
- sabino
54
what causes dominant white
- 34 mutations identified in KIT
W/w
- variable depigmentation 50-100% of skin and hair
- ovverides all other colour genes
55
what causes spotting tobiano
- To/
- colour spotting ( variable expressivity )
- on grey it will eventually turn them white
- 20-80% depigmentation
56
what causes overo
- dominant 1 copy
- recessive lethal
- paint looking
- associated with deafness - a loose association is blue eyes and white ears = deaf
57
what causes splashed white
- SPL/
- associated with deafness
- phenotypic overlap with overo
58
what causes sabino
- 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
what colours lead to death
- RN/RN
- W/W
- O/O
60
what is N+
- postulation
- no white markings/ dominant to Nn
- may modify expressions of tabiano, Sabino, over, and splashed white
61
what causes leppard spotting
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
