Coat Colour Genetics in Australian  Mist
by Truda M Straede BSc PhD
This article is based on that which first appeared in 'Spotted Mist 1986-1996', and has subsequently appeared in a variety of forms in National Cat, and the updated breed book 'Cats in the Mist' (1998), and the 'Companionable Cat' from 2005.

Australian Mist come in six colours, brown, blue, chocolate, lilac, gold and peach. These colours are achieved within the B, C and D series of colour genes, interacting to give patterns with the A and T series.

Considering only the colour loci, B, C, and D, these can be characterised as follows:

B called black, present in all three forms,
 B black,
 b brown,
 bl light brown. B>b>bl.
ie B cats can carry either b or bl as a recessive,
b can carry only bl,
and bl cats are homozygous  recessive.

C called full colour, has at least three recessive forms, the only form in the Australian  Mist is the Burmese form (cb), hence all Australian Mist are by definition homozygous cbcb.

D called dense pigmentation, allows pigment to be evenly dispersed throughout the hairs, its recessive form d, causes pigment granules to clump. This has the effect of turning black to blue, as the clumps refract incident light in a different manner from the dispersed pigment. This allele is know vulgarly as "the blue dilute", colours caused by its presence, dd, would more suitably be called 'clumping' colours. Both alleles are present in Australian Mist, D>d, so that D colours may carry d.

And that is really all there is to it - at least as far as the main genes are concerned.


Possible genotypes of each recognised colour:
Brown B(B,b,bl);cbcb;D(D,d)    (TICA Seal Sepia)                    Blue  B(B,b,bl);cbcb;dd (TICA Blue Sepia)
Chocolate b(b,bl);cbcb;D(D,d)  (TICA Chocolate Sepia)           Lilac b(b,bl);cbcb;dd (TICA Lilac Sepia)
Gold blbl;cbcb;D(D,d)               (TICA Cinnamon Sepia)           Peach blbl;cbcb;dd (TICA Fawn Sepia)

The table below indicates the interrelationships between the two founding breeds and the equivalent self coloured cat (regardless of breed). Colour names used are ‘common usage’.
 

SELF
ABYSSINIAN
 BURMESE
AUSTRALIAN 
MIST

full colour C
burmese dilute cbcb
Genotype
non agouti
aa
agouti
A
non agouti
aa
agouti 
A
B-D-
black
tawny
brown
brown/seal sepia
B-dd
blue
blue
blue
blue/blue sepia
b-D-
brown
chocolate
chocolate
chocolate/chocolate sepia
b-dd
lilac
lilac
lilac
lilac/lilac sepia
blblD-
light brown
cinnamon
no equivalent
gold/cinnamon sepia
blbldd
light lilac
fawn
no equivalent
peach/fawn sepia

To achieve the delicate colouration of the Australian Mist, these main colours which make up both the pattern elements, and the dark tips on the agouti background hairs must be present in sufficient intensity for the colour to be visible - but not in such excess that, for instance, the Burmese brown markings look black, or the lilac is so dark that the cat looks dirty, rather than pretty.

Much of the colouration comes from rufous polygenes, such as those responsible for  transforming the cold coated "usual" abyssinian into the magnificent rich warm tawny of today. Their action is particularly noticeable  on the cat's tummy and chest (creamy, pinky, goldy tonings), across the bridge of the nose, and on the thumb spots on the ears (hazel, rusty, copper tones) and in the pale agouti bands and at the roots of each hair  (cream, gold, apricot, orange brown tonings). The lower parts of each leg, where the background hairs are virtually unticked, also show richness of  toning reflecting the degree of rufous enhancing polygenes present.

The difference between the cool, almost silvery colour of the Singapura, and the top tawny Abyssinian of today - both with the same main colour genes (B-D-C-), lies in the selection for as few rufism enhancing genes as possible in the Singapura, and in the Tawny Abyssinian, as many as possible. At the moment, the Australian Mist appear to encompass almost as wide a range as between these two breeds - with every possible intershade in between.  Selection for improved colour is therefore necessary, and the addition of a new source of rufism enhancing genes, through the use of a new Abyssinian bloodline is timely.

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