Colour Genetics Flashcards
why study colour
- to determine the association of different traits and genes affect other body functions, not just colour
- melanogenesis genes impact additional biological systems
what is eumelanin
black and brown colours
what is phaeomelanin
yellow and red colours
what is melanin
- produced by melanosomes
- found in melanocytes
what causes different pigments
- melanin granule modifiers = the size of the granules and their ability to reflect light
- arrangement in follicles
what are the two base colours
- black/bay
- red
what causes black
-agouti (ASIP)
- homozygous recessie a/a causes black
what causes bay
- agouti (ASIP)
- heterzygous dominant
- A/ dominante for bay
what causes brown
- no evidence for brown
- one additional gene for brown that is recessive
= another gene at agouti causing a different variation of black
what causes chestnut
- MC1R
- e/e homozygous recessive
- no eumelonine, epistativ to agoutie
what casues a dark chestnut
- E/
- heterozygous dominant turning it into a dark bay chestnut
why do red heads need more anasthetics
- 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
what colours are modified by dilution
- cream
- pearl
- sunshine
- mushroom
- dun
- silver
- champagne
what causes cream
- mutation in melanocyte transporter protein gene MATP (SLC45A2)
- transports molecules required for melanosome function
what is cream
- Cr, incomplete dominance over chestnut and bay
- heterozygous genotype
- mutation in melanocyte transporter protein gene MATP
what can cream be expressed by
- buckskin
- palomino
- cremello
- perlino
what causes smokey black
- a/a E/- Cr/cr
- heterozygous
what causes smokey cream (peeling)
a/a E/- Cr/Cr
- homozygous
what causes a buckskin
- heterozygous - bay into buckskin
- A/ E/ Cr/cr
what causes perlino
- homozygous bay
- A/ E/ CR/CR
what casues palomino
- recessive e/e
- heterozygous on chestnut
- e/e Cr/cr
seen in mane and tail
what causes cremello
homozygous on chestnut
- e/e CR/CR
- distinguished through lineage or DNA testing
what casues pearl, sunshine and snowdrop
- recessive mutations in MATP
what is pearl
- recessive pearl (prl) dilustion mutation affects eumelanin and phaeolmelanin
what causes black pearl
- homozygous recessive (mutation)
- a/a E/ prl/prl
- seem generally in quater or iberian horses
what casues bay pearl
- A/ E/ prl/prl
- homozygous recessive
- more extreme dilution
what causes a chestnut pearl
- e/e prl/prl
what causes sunshine
- believed to behaved like prl
- no homozygous identified
- mutation identified in conjunction with CR
- e/e CR/sun
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
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
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
what colours blue/black dun and Grullo
- a/a E/ D/
- characterized by back stripe and leg stripes
what causes yellow (bay) dun
- A/ E/ D/
- dun on bay
- black hair and tail, back stripe and stripes on legs
what causes red dun
e/e D/
- some dilution of coat colours and stripe with leg stripes
what causes silver
- silver dilution mutation (z) is dominant if base colour is black or bay; no effect on chestnut
what causes silver dapple
- a/a E/ Z/
- largly seen in mane and tail
- silver on black
what causes red silver dapple
- A/ E/ Z/
- silver on bay
what causes icelandic horse
- e/e Z/
- chestnut
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
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
what causes champagne black
- a/a E/ CH/
what causes amber champagne
- A/ E/ CH/
what causes gold champagne
- e/e CH/
- coloured hair on pink skin
what is roan grey
- intersperse coloured hair
- added in white hairs
what causes progressive whitening
- a/a E/ G/ - white on black
- A/ E/ G/ - white on bay
what causes roan chestnut
- e/e G/
- progressive whitening
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
what are the grey rankings for melanomas
- grey on black
- grey on bay
- grey on chestnut (homozygous)
- grey on chestnut ( heterozygous)
what causes black(blue) Roan
- a/a E/ RN/rn
what causes bay (red) roan
A/ E/ Rn/rn
- scars and scrapes will return fully pigmented
what causes strawberry roan
- e/e RN/rn
- they appear lighter becasue of hair is into mingled
what are the different depigmentations
- dominant white
- tobiano
- overo
- splashed white
- sabino
what causes dominant white
- 34 mutations identified in KIT
W/w - variable depigmentation 50-100% of skin and hair
- ovverides all other colour genes
what causes spotting tobiano
- To/
- colour spotting ( variable expressivity )
- on grey it will eventually turn them white
- 20-80% depigmentation
what causes overo
- dominant 1 copy
- recessive lethal
- paint looking
- associated with deafness - a loose association is blue eyes and white ears = deaf
what causes splashed white
- SPL/
- associated with deafness
- phenotypic overlap with overo
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
what colours lead to death
- RN/RN
- W/W
- O/O
what is N+
- postulation
- no white markings/ dominant to Nn
- may modify expressions of tabiano, Sabino, over, and splashed white
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
