Dominant + dominant = evidence of
the dominant;
Dominant + recessive = evidence of the dominant;
Recessive + recessive = evidence of the recessive.
1.
THE "B" GENE (the Black series)
This is the gene that gives the black colour, and also the liver one!
Both colours are due to the same pigment (eumelanin) and the size of its
particles determines whether it is seen as black or liver. The gene for black is
designated by "B" (=dominant), while the one for liver is designated by "b"
(=recessive). If we have parents ... father=BB (=black) ... mother = bb
(=liver), all their offspring will be uniformly "Bb".
As we
explained above, the dominant gene masks the expression of the recessive, so
this first generation offspring will be uniformly black, all the puppies
carrying a "Bb" gene sequence.
If we mated the first generation pups to each other, the offspring in this
second generation would each show one of these combinations:
Bb + Bb = BB which is black
(homozygous)
Bb + Bb = Bb which is black too (heterozygous)
Bb + Bb = equivalent to the above line
Bb + Bb = bb which is liver (homozygous)
BB and Bb are "phenotypes"
(physically black but there is no guarantee of the genetic combination), while
"bb" is a "genotype" (liver is ALWAYS and ONLY of "bb" type).
Also it should be noted that, statistically, a mating as above (Bb+Bb) will
produce 75% black coated offspring, and 25% liver. However, on a small amount of
offspring, it may not be true, of course! (For another characteristic -
tricolour - when I bred together a dog and a bitch both carrying the tri gene, I
had to wait until their third litter to obtain tri-colours!)
Hard to understand? Sorry, but if you did not follow, please read again,
otherwise the next steps will be unintelligible.
2. THE "A" GENE (the Agouti series)
There are several forms of this gene, several "alleles", but we are fortunate in
that our breed only involves two of them: "As" and "at". (Although one expert
thinks there is a possibility for a third allele for "A" in the Brittany.
Despite my investigations, I could not find any evidence of this theory, while
my conclusions appeared to be correct, after a check on about 500 Brittanys!)
"As" which is dominant, gives solid colours, while "at", which is recessive,
involves the "tan point" that gives the ticking at the end of the legs, around
the anus, on the eyebrows, and on the cheeks. In short, it qualifies our
tricolour dogs, while the "As" gene concerns the non-tri's.
As seen before, the combination of the two genes give: