|
 The
particularity of the silver gene is that it changes it's' name according
to
the cat that
carries
it :
on
a tabby, it will
become a
Silver
Tabby whereas
on
a
non-tabby
it
becomes a smoke.
The silver
gene is identified by the symbol
"
I ". It is
responsible for blocking the synthesis of the yellow pigment, called
phaeomelanine,
the
basis of solid colours, and
replacing it
with
a luminous white pigment.
The
Chinchilla and Cameo are
silver tabbies in which "Wb" has modified the tabby. As we learned during the
study of the tabby, the wild gene "i+" has not impact.
A
silver cat may be :
ü
"II":
silver
homozygote :
all kittens will be silver, or
"Ii+" :
silver
heterozygote, in which
only half the litter, coming from a non-silver, will be silver
Example
1 :
A breeder
regularly marries his golden shaded female with his neighbours' golden male. Out
of three litters came ten golden kittens. The fourth litter however produced
three chinchillas or silver shaded kittens. What happened during the fourth
litter ?
Example
2 :
A breeder
marries his two brown mackerel tabbies Norwegians. The litter consists of two
brown mackerel tabbies, one brown blotched tabby and one silver mackerel tabby.
He is sure of the parents' identification. What can we assume in this
case ?
A
no-silver cat
"i+i+"
will only give a silver kitten if bred with a silver cat
ü
The
cross-breeding of two silver homozygotes (II x II) will only produce silver
homozygotes kittens.
ü
The
cross-breeding of two silvers, one of which is a homozygote, (II x Ii+) will
produce silver kittens, yet half of these will be heterozygote.
ü
The
cross-breeding of a silver homozygote and a solid (II x i+i+) will give 100%
silver heterozygote.
ü
The
cross-breeding of two silver heterozygotes (Ii+ x Ii+) will produce 3/4 silver
for 1/4 non-silver.
ü
The
cross-breeding of a heterozygote and a non-silver (Ii+ x i+i+) will produce half
silver and half non-silver.
The cross-breeding of two non-silver (i+i+) will produce no silver
kittens
Answers
to the exercises proposed by Alyse
Brisson
Example
1 :
In no way can
the golden shaded male be the father of this litter. The female had mated with a
chinchilla or a silver shaded.
Example
2 :
If
neither of the parents are silver, a silver kitten cannot be produced. The
silver gene is dominant and cannot, under any circumstances, skip one or more
generations. The Norwegian coat is not selected upon a "warm tone" criteria and
"cold-coloured" brown tabbies are quite frequent considering the natural biotope
(habitat) of this cat. The same situation does not apply to the Maine Coon who
comes from a region where a red and rust-coloured environment is
common.
|
RETURN SUMMERY GENERAL
Why are
the phantom markings so visible on the smoke ?