PART 3 – SOME PATTERNS
by Sheila Sowter
This is a minefield since we have on the one hand standardised and unstandardised varieties (phenotypes) and on the other we have
the genotypes (what the genes command). They don’t match well.
Let’s clear some varieties out
of the way. Siamese and Himalayan (see part 2) are not regarded as ‘marked’ (in
some countries they are classed as ‘shaded’). Most but not all marked rats,
which have coloured areas and white areas, seem to be produced by variations on
the H locus.
In marked rats in most cases
both the genes on the H locus affect the pattern. What follows is based on my
own breeding and may contradict what has been published elsewhere.
H is the self gene and an HH
rat is a self and should have no white, though minor genes may produce white
toes or a few white chest hairs. h is the hooded gene and an hh rat is a hooded
and an Hh is one type of Berkshire, often with little white on the belly.
The ‘Robert gene’ may or may
not be the same as Hre restricted, which is in the American
scientific literature. For this article I shall call the gene Hro.
It is homozygous lethal (Hro Hro are born dead or dying) HroH
is the Robert-type Hroh is Baldie which for years was dismissed as
‘mismarked capped’.
HI is the Irish gene
which is responsible for the Irish pattern. It seems to be a distinct gene
since I have been getting litters with more Irish kittens than would be expected
if there was not a distinct gene. How it combines with other genes is
work-in-progress. There seem to be at least two different genes giving the
Irish pattern.
Hc is my notation
for the capped gene which gives capped rats when homozygous hchc.
You will not find this in the literature but my breeding and that of other
breeders agrees with this. Hhc is a bad Berkshire with wiggly edges
to the belly white, hhc is a poor hooded with a white throat and a
few spots rather than a full saddle. Hrohc gives a rat
with a little colour on the head or none at all, which is a black eyed white.
Husky rats can be produced in
several ways. The usual silvered husky in Britain is produced by a single
recessive gene. A rat with similar markings but without silvering is produced
by the Robert gene with at least one other gene, and huskys in the USA are said
to be produced by a single dominant gene.
Blazed rats are produced by a
combination of genes, bareback and variegated are probably produced by several
genes or at any rate some heterozygous combinations, but this is
work-in-progress.
There are a lot of areas of
debate and uncertainty and I hope to mention some of these in the last part.
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