Build-A-Calico-Cat Part 2

Following the instructions in Part 1, you will now have in your Petri dish a bald pink quadriped foetus. Still developing are the gustatory and sensory apparatus (visual, auditory, olfactory) at the head end, and locomotory power, excretive and genital tracts at the rear. She's cooked and ready to now be dressed in Her calico epidermal coat, (a tricolour ginger, black and white) peculiar to Her XX (in mammals, a female) genotype. Coat colouring patterns and texture are peculiar products of refinements and adornments executed in production of the full-term kitten.

Calico-Coloured Cat Assembly, Part 2:
In attempting assembly, consider Her coat’s colour and texture gradients. She’s longhaired, but this coat shows distinct geographical differences
i) a basic right/left symmetry (shared by all vertebrates, split by their spinal cords)
ii) head to tail asymmetry (sensorium at the front to functionality [excretion, reproduction, locomotion] at the rear)
iii) dorsal/ventral asymmetry
iv) distal pattern distributions

After i)'s structural imperatives, (a primitive remnant for Chordata), Her texture and colourways follow ii), iii) and iv). For texture there forms a 3-D gradient with short glossy hairs on Her mask but flagrantly long whiskers and mane, and fluffy trousers, interdigital spaces, tail and underbelly. She's short, glossy and dark at the tip and along the top, and fluffy and pale on the underbelly and tail. In some doubled-dosed ventral fields, (bilateral axillary and nipple lines, pelvic areas, her fluffy hair underside hair becomes curly. Very similar to the distribution of human secondary s*xual characteristics. Thus Her colour and hirsute texture axes show head/tail, trunk/extremities and endo/ectoderm polarities, with distributions across x-, y- and z- axes.

How did she get tricoloured, with a white belly and a patchwork of black and ginger on her dorsum? These darker spots aren't always symmetrical, because they're displaying 'field' properties through discontinuous spotting of selective coat-colour phenotypes across somatosomes. Her white belly and underside is a product of common, primitive dorsal/ventral asymmetries, where the agouti-repressing white colour is promoted by through ventral and distal gradients. The black spots on her mask, back and tail are also products of patchy expression of a dominant melanin-producing genes, controlled by 'spotty' field properties.

Her mosaic topside of ginger and black reflects a battle between a wild (ginger agouti) and a mutant (black) colour gene. In a tom, the black gene on his single X chromosome remains unbalanced with no corresponding gene on the Y, producing a black-topped kitty. In XX females, a counter-balanced wild, agouti ginger allele on the second X assumes partial penetration, producing Her Rula Lenska-esque, bi-colour, black and ginger tortoiseshell top-coat with a white underbelly, and particularly fluffy hair in endodermic intrusion fields. Her wonderful coat would make an elegant handmuff (one can't help but speculate) in some kind of affectionate, recycling spirit.

An addendum on agouti-patterned ginger colouring-
http://www.fanciers.com/other-faqs/color-genetics.html

Informative slide lectures on feline coat genetics here:
http://www.janecky.com/runyen/bio554/cat/INDEX.HTM
Short guide to tortoishell (not calico) at wikipedia, here