[Mike1975]

Thank you Phil for your reply!

This site for havanese and some other sites for poodles, were the reason I asked about the V gene (silvering gene).

Havanese and poodles also carry the Graying gene but its effects is somehow different than in yorkies, considering that both breeds have double coats instead of the singe coat found in our breed. Also they carry different alleles in other locii, so the final result is completely different.

In this quiz answer Quiz # 2 answer it says :

"TIERRA started life as a Black and Tan puppy with extensive markings in a pale golden colour. She appears to carry the Saddle Tan variation which has faded her coat from the front to the shoulder leaving her head and front light coloured and her back and rear dark coloured. The chinchilla gene is very prominent and started work early to lighten her tan to creamy white. The silvering and greying genes played a large part in her colour change as well. The silvering gene has lightened her black to pewter and the graying gene has liberally interspersed it with silvery white hairs."

In a poodle site Color Genes in the Poodle I came across this :

"Most authorities describe a dominant allele (G) for graying; non-gray would be gg. Some also consider it to be the gene for silver, in which case it would have to be a partial dominant. Willis (1989), however, says that silvers are dilute grays (ddG_; he does not indicate whether ddGG and ddGg would be the same). Searle (1968) says simply that "this dominant gene apparently leads to a progressive graying in coat-color throughout life and seems to be present in poodles."

My own study of standard poodle pedigrees is consistent with the interpretation that gray and silver are separate genes. To avoid confusion, let's call the silver gene V . This gene shows incomplete dominance. In other words, if a poodle that is VV would be black, Vv would be a dark blue-gray and vv would be silver. Both blues and silvers are born black. Silvers "clear" during the first year. This involves the gradual loss of pigmentation from about 90% of the inner coat (hairs become transparent or white, depending on thickness), but a substantial percentage of the outer, guard hairs retain some color."

It seems that havanese and poodles carry both genes (G and V) and their combination alters the final phenotypic result.

To add a little more confusion, Joan Gordon claims :

The next gene you need is the one that assures the age at which the blue skin will retreat from the head allowing only the gold to grow and a gene to tell your black puppy that it is time to kick in the color pattern in each hair for the blue. Connected to this is the gene that tells the dilution factor to stop at a specific color and to maintain it at that color.

Color & Texture by Joan Gordon

Many stunning yorkies have maintained their TRUE (not enhanced) deep dark blue color to the age of 5 and sometimes later. On the contrary there are specimens that cant hold color up to 2 years of age. The blue dillutes and dilutes to a silver color and finally we come up with an almost white dog. Most of these dogs have routs of a darker color, but as the hair grows the dilution factor is so strong that can't hold correct color. Additionally these dogs have super silk quality, and amazing texture.
Somehow dilution factor of the Graying gene or the V gene or maybe both of them are connected to texture.
Moreover it seems to be a connection between gold and blue - in other words phaeomelanin and eumelanin.

To quote again Joan Gordon from http://dandugmore.netfirms.com/color.html:

"Since a Yorkie is actually a brown dog with a blue saddle- just as an Airdale and many other breeds are. They only way you can lighten or darken your dogs color (I do mean the blue as well) is to plan your breeding on the color of the gold. The blue color and the gold compliment each other. Light gold equals light blue - rich gold color equals dark blue. Bred this way they can pass it to the next generation. Lots of you do this without knowing it. Gold is the first thing anyone checks on their newborn puppies"

My -short- experience with the breed, confirms Joan Gordon.
Light gold = light blue and rich gold = dark blue.

BUT on the other hand there is another cause of silver color, and that is lack of pigmentation in general. This can easily be seen if we check the skin under the blue, which should be pink instead of blue, or a very very light blue, meaning that there is not enough eumelanin.

It is also very interesting that both colors are connected through the patterns of each other - controlled by A locus. The allele responsible for their tan pattern is [As] (saddle tan) according to Malcolm Willis. Tan on the forelegs extends up to the elbow and on the hindlegs it extends from the foot to just below the stifle. As you have mentioned in a previous post, the tan is not coming up quite as far on the body as in other saddle tan breeds.

Under the blue coat, the skin has a bluish tint and under the tan coat the skin is pinkish in color. If the pink skin invades the blue skin or vise versa, we will get an unclear gold and an incorrect blue.

So how can we explain all these genetically?

As for the hypothesis concerning the incomplete dominance of Graying Gene, it can be probably explained through Red Legged yorkies.
I hypothesize that a Red Legged is a [gg] dog. When bred together they of course reproduce themselves (recessive homozygous) , but when bred with a [GG] dog they can produce a [Gg] dog.

Thanks again
Mike