A Locus
Lesson #4 will be based on the A Locus. The A Locus attained it's name from the word Agouti.
Fawn and White Boston Terriers, sometimes known as sable, are one of the two most complex colors of the Boston Terrier
rainbow, the other being seal.  There are multiple color genes responsible for the coloring of a fawn Boston Terrier making
it nearly impossible to even DNA test for the coloration.  

Like all colors of Boston Terriers, fawns are no different. There are many shades of fawn, from extremely light base fawn to
a rich/vibrant red base fawn coloring.  The most distinct attribute that fawn's posses, is their masking and banding of darker
hairs throughout their coat.  As with the varying hues of fawn color there is also varying degrees of sabling on different
shades of fawn. Their hues truly vary depending on how much masking or darker colors they have through their coat.

The best way to describe a fawn Boston Terrier's coat is a fawn base color with intermingled black hairs, as well as hairs
that are "banded". Banded is a term meaning that the hair is fawn at the base and black at the tip which may seem almost as
a reverse seal (black base with reddish tinted banding at the tip). There are fawns with minimal masking and minimal
banding as well as fawns with no masking at all! Puppies are sometimes born with so much banding and black hair that they
appear brindle until a couple of days or even weeks later.

Most fawns have a visible and distinct melanistic mask, genetically coded as Em. The black mask is formed as an interaction
between the MC1R or E gene with the agouti protein and melanocyte stimulating hormone.
It is very important to note that melanistic masks can be found in colors other than black, including, brown and grey. There
have recently been more of these oddly colored fawns being produced: lilac/fawn, chocolate/fawn, etc.
Fawn and White
Genetically Known As:  K/K, a/y a/y, Em
***These Boston Terriers are NOT Seal and White***
-The predominant pigmentation of fawns is black however there are also fawns with red pigmentation
(red/self colored paws/nose)  known as red fawn or chocolate fawn and diluted pigmentation that are
known as blue fawn and lilac fawn. Pictured below left is Becks, a red fawn Boston Terrier from Little
Lerma's Boston Terriers. The middle and right photos are of the same dog, a chocolate fawn Boston Terrier
from Beryl Boston Terriers.





















-There have been fawn colored Boston Terriers that have no melanistic mask or banding. This is known as
a "clear" fawn and can easily be confused with a dark cream known as a honey and white. To verify whether
a Boston is a clear fawn or honey a DNA color analysis can be performed for the E locus. If double "
e" does
not result (e/e) for E testing the dog tested is not a cream/honey and is in fact a clear fawn. There is not a
single test that determines fawn available from any DNA coat color testing facility/laboratory. The reason is
because fawn is a coat color that is made from many recessive alleles and is extremely complex.  Admittedly
I only know the minimum of fawn genetic information but I am happy to refer anyone who is seeking more in
depth information to more knowledgeable parties. info@cypressfarmkennel.com
***Important Facts To Note About Fawn Boston Terriers***UPDATED 9/29/15
I am ready to move onto Lesson #5: E Locus
Please Take Me To Lesson #5        Please Take Me To Color Home
Thank you to Gabby's Fawn Bostons for allowing us to use their puppies/dogs photos as examples for
our A locus lesson. You can see more of Gabby's dogs here:
http://www.gabbysfawnbostonterriers.com/