THE COLOURS OF THE BRITTANY
(The Genetic Transmission)
I AM NOT A GENETICIST!.... but I am
very curious, and as we poor Frenchmen, dispose of very few popularizing
literature about the subject, a few years ago, being unable to find someone who
could help me with the mystery of colour inheritance, I undertook an
investigation in the works of some writers in your language, and after a lot of
reading and investigations, I wrote an article about the subject, that has been
printed - in French, of course - in the Club de l'Epagneul Breton magazine in
1991.
Since then I went on investigating ... and, as I believe many of you have as
little knowledge as I had, I hope that this article will help you understand how
things work for our specific breed.
Before starting to "teach", a few words more:
For those who do not know yet, the French standard admits five colours, with or
without roan:
Orange and white (OW)
Black and white (BW)
Liver and white (LW)
Tricolour black (Black + white + orange: BT)
Tricolour liver (Liver + white + orange: LT)
It is impossible to try and explain
genetic transmission without some preliminaries. Even avoiding the technical or
trying not to take myself for a scientist, a minimum of knowledge is
indispensable. Any dog of any breed, even mongrels, possess the entire panel of
the genes existing in the species. Whether it is physically visible or not in a
specific dog is another question, but the fact that a gene is not physically
visible does not mean that it is not present! Most of the visible
characteristics of a dog (the "phenotype") are under the influence of genes,
present in the chromosomes, and so inherited from the parents. Some are not as
they depend much of the way the dog is raised: weight, coat thickness,
occasionally also height, musculature, etc Genes are always present in pairs,
one of the elements of the pair coming from the father, the other one from the
mother, due to the division of the cell at the time the embryo is created. To
give a rough example: If the father's genes are imaged by "PP", and the mother's
genes by "MM", the offspring will carry "PM" genes. Those genes may exist as
several varieties (the alleles) for a same gene, whose influence varies
accordingly in its effect as well as strength. We distinguish DOMINANT genes,
and RECESSIVE ones. (This notion of genetic dominance must not be confused with
the "dominance" of a temperament. "Dominance" is a word for the genetician,
white "domination" involves social characteristics). By convention, a dominant
gene is designated by a capital letter, white a recessive gene is designated by
a small letter.
The existence of a dominant
gene is ALWAYS evident, visible; people say that the gene is expressed. Even if
the pair of genes consist for one half by a recessive, and for the other half by
a dominant, it is only the latter that will be in evidence, and not some
intermediate between the two genes! On the contrary, for a recessive gene to be
expressed, this one will have to be present in double (="homozygous"). In short: