Coat Color Inheritance in Italian Greyhounds
In this article gene theory as it relates to Italian Greyhounds will be discussed. Only the bare essentials of the issue will be explored. Readers are encouraged to read in depth books and articles on inheritance of coat color.
Coat color in dogs is controlled by approximately 9 series of genes. Fortunately there are few dogs which are homozygous to one color. Unfortunately the genetics of coat color in Italian Greyhounds is not a simple issue in which only one or two alleles control the outcome of color. Several factors must be taken into account when studying color outcome in IGs.
A Genetic Primer
"A" - The Agouti Series
The genes which form this series of multiple alleles influence the amounts and location of dark or light pigment in the individual hairs of the whole coat. The following is the list of alleles in dominant order:
A - Allows the distribution of dark pigment over the whole body.
ay - restricts the dark pigmentation and produces what we call red or red sable.
at - produces the bi-color we commonly call "black and tan" (blue and tan, red and tan, etc.). This allele is only included because of the possibility that this color exists. Modern breeders are breeding away from this color combination because the breed standard does NOT include it. IGs which present this color combination are disqualified in dog shows. It is most probable that this allele no longer exists in Italian Greyhounds but since it is a recessive gene, it may still be lurking in some bloodlines.
There is also another allele to this series but will not be discussed here as it is not present in Italian Greyhounds.
"B" - B Locus
This is perhaps the most well known series of genes in dogs. Only two alleles exist for this series.
B - Produces black pigment and black coat.
b - Produces brown pigment and brown coat.
More than likely Italian Greyhounds are homozygous for BB. While there have been reports of some "chocolate" (bb) Italian Greyhounds this may be due to a mutation in the "b" allele. This is only carried in certain bloodlines of Italian Greyhounds. There have been rare reportings of true chocolate Italian Greyhounds. These dogs will always display a brown nose. Most IGs currently called "chocolate" are more than likely a variety of what is known as "seals" if the nose pigment is black.
"C" - Albino Series
The genes which form these multiple alleles influence the depth of pigmentation. This is perhaps the most interesting series. This series could explain the variety of "shades" we see in Italian Greyhounds. Nose pigmentation is not affected by this series.
C - allows full pigmentation. Deep reds, deep blues and deep blacks best illustrate the affect of this allele on coat color.
ch - suppresses the pigmentation: creams, light fawns, light blues. This gene does not appear to have an affect on black coat.
There are other alleles to this series but are not known to be present in Italian Greyhounds. Although the cd allele in this series is known to produce white coat with black pigment and Italian Greyhounds are known to sometimes appear in this color it is more than likely such a dog is actually produced by another gene called the spotting or "S" series. The spotting series will be discussed later.
"D" - Dilution Series
Only two alleles exist for this series. This series does not cause color but acts upon other loci to cause different expression of those genes.
D - intense pigmentation
d - dilution of pigment.
If the "D" is present either singularly or duplicate, the color of the coat will be expressed by other loci. If the "d" is present in duplicate then the coat color will be diluted. The degree of dilution will depend upon other loci and modifying factors.
"E" - Extension/Restriction series
There are multiple alleles to this series but only those relevant to the Italian Greyhound will be discussed. This series either extends dark pigment or restricts dark pigment.
Em - Dominant to all other alleles in this locus. This gene produces the black mask seen in some Italian Greyhounds. This mask is best seen in fawn or red colored Italian Greyhounds. The mask is usually on the muzzle and extends up the face. A black Italian Greyhound may carry this gene but it may only be expressed in a light colored dog.
E - Allows the extension of dark pigment without a mask.
e - restriction of dark pigment. If a dog is carrying black this allele will not show black except for nose pigment.
G - greying series.
All Italian Greyhound's are homozygous for "g'. The dominant "G" causes progressive greying of the coat as seen in Kerry Blue Terriers. These dogs are born black and as they age their coats turn grey. There have been no reports of this occuring in Italian Greyhounds.
"S" - Spotting series.
Here are several alleles to this locus. This series controls the amount and expression of white markings.
S - solid color. Modifying factors may influence the expression of a small patch of white seen on the chest, or white toes.
si - irish spotting. This is a definite pattern with white appearing on the muzzle, chest, legs, neck and tail. Modifying factors control the amount of white seen. Plus factors may extend the white up the legs or cause a large "collar" of white around the neck. Minus factors may restrict or cause no white collar around the neck but allow white boots upon the legs.
sp: piebald. This is where white covers 50% or more of the body. Plus and minus factors influence the amount of white seen.
sw - extreme piedbald. Usually this is an all white animal. Plus factors may cause the ears, eyes or head to be colored. This is not a common gene in Italian Greyhounds. Most whites with colored heads are more likely to be sp in origin with modifying factors creating mostly white. There are a few bloodlines of Italian Greyhounds that do carry the sw allele.
T - Ticking Series
There are two alleles to this locus. Flecks of color will appear in white areas. The most well-known breed for this series is Dalmations.
T - produces the ticking.
t - no ticking will be seen.
Ticking is not necessarily present at birth but as the dog ages flecks of color will appear within the white areas of the dog. The color that appears will be the base color of the dog. In Italian Greyhounds ticking seems to be only of the skin and does not change the color of the white hairs.
The Colors of Italian Greyhounds
Below is a description of the author's opinion on a genetic theory of color in Italian Greyhounds.
A black Italian Greyhound may not be homozygous for the color black. The following assumes the dog will be solid black and only produce solid black:
The black is caused by the A in combinations with the B, D and E locus. The lack of white is controlled by the "S" locus.
An interesting note is that some black Italian Greyhounds have a red/taupe cast to their coats. Clarence C. Little, author of Inheritance of Coat Color in Dogs, stated that dogs with the Aay combination will show a red cast to their coats. Perhaps in Italian Greyhounds those carrying the 'ay" gene will display this red cast. This may well explain what Italian Greyhound breeders call "off black" or "seal". Some Black to red breedings have produced this black with red cast to the black coat. More than one breeder claims this is a way to tell if a black Italian Greyhound is carrying the red gene. The red cast sometimes seen in a black Italian Greyhound could possibly be explained by the interaction of the A ay genes.
There are many theories about the cause of this coat color. One good possibility is that the seal coat is actually a black coat with incomplete dominance. In this case the additional genes cause the "seal-like" color to come through. Perhaps the combination of Aay in addition to the chinchilla gene (ch) causes the familiar seal color to come through the coat. It may be possible that an addition of the Ee locus will cause more "red/taupe" color to appear in the coat.
There is also a color that may be referred to as "off black". Dogs of this color appear to be almost black but just a "shade" away from a true black appearance. There is almost a brown undertone to the coat but the brown will only show in direct sunlight. In the house (indirect lighting) they will appear black. Off blacks are perhaps caused by the Aay alone.
Because of the incidence of red to red producing black it is highly probable that two different types of red coats exist within the Italian Greyhound. Ayay and AAee are the two possible combinations for the color "red" in Italian Greyhounds. When these two types of genes are crossed the resulting AayEe would be an off-black dog.
In most breeds the sable coloration (red with black hairs) is caused by the ayay genes. Modifying genes would perhaps explain why some dogs are more heavily sable (black hairs dispersed through the coat) than others.
As with the red gene it is likely that red fawn has two different genetic combinations. The chinchilla gene acting upon the red coloration produces a more fawn-like appearance of the red - ayayCch.
Italian Greyhounds display two different types of fawns (in addition to varying shades of fawn). Fawns are probably influenced by the action of the chinchilla gene (ch). It is probable that the fawn is a product of the AACchee variety. Another likely combination is the 'e' series reflecting on the ayay combination or ayaychchee variety.
Fawns with blue noses are caused by the dilution (D) series. It is probable that a dilute fawn is caused by the AACchddee or ayayCchddee. Cream or very light fawn with black nose would be of the AaychchD?ee or ayaychchD?ee variety.
As in sables ayay genes cause red with black hairs. It is probable that the "d" series acting on the ayay gene dilutes the black hairs as well as nose pigment. The "e" gene affects the red hairs thus producing fawn. Therefore it is possible that the genes for blue fawn are ayayddee. The paleness of the colors would be influenced by the chinchilla gene.
While combinations are possible on other loci the main locus of the color blue would be the dilution (d) series. A possible genetic code would be AaddE?. The variety of depth of blue can be caused by other genes such as the chinchilla. Therefore a dark blue could possibly be AACCddE? while a pale blue could reflect a combination of AachchddE?.
Chestnut is more than likely a combination of modifying genes to darken the pigmentation of a red dog. This combination would most probably have a similar genetic code to that of a red Italian Greyhound.
A true chocolate Italian Greyhound will have a brown nose. The possible genetic combination for a chocolate would be AabbD?E?. The depth of the chocolate color would be reflected by other combinations within the series. For example, a pale chocolate may closely resemble a fawn Italian Greyhound if the combination of Aaybbddee were involved. In such cases the nose would be very pale in color and display almost a pinkish cast. This is considered a fault in the breed standard. More than likely the eyes would be extremely light in color (also a fault). Some seal Italian Greyhounds have been mistaken as "chocolate" but unless the nose is brown it is probable that the dog is seal with modifying factors involved.
PUTTING IT ALL TOGETHER
To understand how these colors interact with each other, here are some possible genetic combinations:
A seal dog with a genetic combination of AayBBCchDdEe is bred to a medium Blue colored AABBCchddEE.
The resulting prodigy can be (listed below is not all the possible combinations):
AayBBCCDdEe (off black)
AayBBchchDdEe (Seal with lots of taupe showing)
AayBBCchddEE (medium Blue)
AayBBchchddEE (light blue)
AayBBCCddEE (dark blue)
AABBchchddEe (light blue)
If the blue were AayBBCchddEe bred to the same seal dog it is possible to have a variety of combinations
ayayBBCCDdee (red-fawn) -
ayayBBchchddee (pale fawn),
and other combinations.
It is important to remember that in any one breeding of the dog, the possible outcomes would not be seen in one litter.
Therefore, one could have a whole litter of blues or of one black, one fawn, and several blues.
In conclusion color genetics is an extremely complex issue.
The above discussion barely scratched the surface. Please consult such authorities as:
Malcolm B. Willis - Genetics of the Dog
Clarence C. Little - The Inheritance of Coat Color in Dogs