Many Breeders and potential buyers are looking
for color (referring to any Pinto color) when
looking at the Gypsy Horse or Drum Horse. We put
together the following basic Genetic information
to help those interested in the colored Gypsy
Intro to Genetics - Because
there are many variables when dealing with genetics
we will cover only the basics. While on this topic...forget
about the genetic color White!
What is a “gene”?
A bit of DNA which acts as a code to control part
of a cell's chemistry, such as producing proteins.
What is an “allele”?
One form of a gene.
What is meant by Dominant? An
allele that always expresses itself when it is
partnered by a recessive allele or by another
What is meant by Recessive? An allele
which only expresses itself when it is partnered
by another like itself.
What is Genotype? The type of
alleles present for a particular Gene or genes,
for example Tt
What is Phenotype? The way a
gene works or expresses itself in practice.
Here are a few facts when looking at genetics.
Genes are found on chromosomes. There are 64 chromosomes
found in today’s horse! There are Dominant
genes, represented with a capital letter, and
Recessive genes, represented by a lower caps letter.
32 chromosomes are inherited from the stallion
and 32, inherited from the
at color genes...
- represented by the letter T. (Most common pinto
color when referring to the Gypsy Horse)
Tobiano is a Dominant gene, meaning only one Dominant
T gene needs to be passed on for the foal to display
the Tobiano pattern. For example...if you have
2 Tobiano Horses both are genotyped with Tt, your
chances of getting a Tobiano foal is 75%. In other
words, in a perfect world, 75 out of 100 horses
would be born displaying the Tobiano pattern.
However if the resulting foal were to inherit
only the t—or recessive Tobiano gene from
both parents, although genetically still a Tobiano,
it will be a solid color! Now, if you have a mare
or stallion that have two Dominant T genes or
TT, (also known as Homozygous), you will have
a foal that is Tobiano no matter what you breed
to, ideally. If you were to breed a Tt (horse
displaying the Tobiano pattern) to a tt (a Horse
not displaying the Tobiano pattern, but still
genetically a Tobiano) your chances of getting
a colored Tobiano horse is 50%.
by the letter O.
Overo, also thought to be a dominant gene, follows
basically the same rules as Tobiano genes, with
few exceptions. So if you have an Oo foal it will
display the Overo coat pattern. Oo will be a horse
of solid nature. OO, Homozygous, is lethal. The
foal will either be still born or die shortly
after birth. This is know as Lethal White Overo,
unfortunately there seems to be little information
as to why.
It is important to note that there is not as much
know about the Overo genetics as there is the
Tobiano. It is thought that Overo may be caused
by as many as 10 genes. There are documented cases
where and oo solid horse has produced an Overo
pattern from a genetically solid horse! This would
suggest the Overo is recessive!
The Homozygous Horse.
Homozygous refers to a horse that has two of the
same dominant gene. For example TT. This horse
will pass on one Dominant T gene no matter what
other genetic cross. It is important to note that
horses determined to have both Homozygous genes,
do not necessarily always throw the visible coat
pattern. There are many documented cases of Genetic
homozygous horses producing a few solid offspring.
Currently there is not a laboratory test to identify
the presence of the tobiano gene. Genetic markers
linked to tobiano may help, but they cannot prove
homozygosity since they are not direct tests for
the tobiano gene.
Homozygous tobianos are identified on the base
of evidence, via Progeny tests!
To qualify as a homozygous tobiano a horse must
be the result of a breeding from two tobiano parents.
The horse should have a characteristic tobiano
pattern including ink spots.
Breeding this animal should produce all tobiano
foals with the exception of a rare minimal white.
A horse that produces five tobianos out of five
solid mates is thought to have a 97% chance of
being a homozygous tobiano.
- The alternative forms of each gene are called
alleles. If both alleles are identical, then the
horse is said to be homozygous at that gene; if
the alleles are different, then the animal is
said to be heterozygous at that gene. Both sets
of genes function simultaneously in one cell.
Often when the gene pair is heterozygous, one
allele may be visibly expressed but the other
is not. The expressed allele in a heterozygous
pair is known as the dominant allele, the unexpressed
one as the recessive allele. The presence of a
recessive allele may be masked by a dominant allele,
which leads to the expression "hidden recessive."
Dominant alleles are never hidden by their related
recessive alleles. This may help explain why a
Homozygous horse may occasionally throw solid
*Tobiano - (pronounced: tow
be yah' no)
The pattern of a tobiano is evident from the moment
of birth. The white areas characteristically cross
over the topline and produce four white legs at
least below the knees and the hocks. It is almost
unheard of to see a Tobiano with solid legs!
*Overo - Also apparent from
birth, the white color seems to go from the belly
up! These horses will have no white crossing the
topline of the horse. They also may have solid
legs and generally have a nearly all white face.
It is also common for the Overo horse to have
a least one blue eye!
Well genetically speaking, The Blue color is
caused by the Dominant "Roan" gene R.
While "Blue Roan" is similar to grey
in that they share individual white hairs spread
throughout the coat - They are two different colors,
caused by two different genes! Grey is caused
by the Dominant Grey gene G. In normal situations
a Blue Roan, must have Black legs, Mane, tail
and head! However when you infuse the coat pattern
Tobiano or Overo, what is the norm is changed
a bit, because Tobiano patterns horses rarely
have solid legs, manes or tails. For a horse to
be considered "Blue" it must have a
Roan gene present and it must be Base Black (EE
or Ee)! If a horse is lacking pigment under the
coat hair (the skin is white, not black) the horse
can not be considered "blue".
Notes:-With very few exceptions, you will not
see a Homozygous Roan. A foal born with two dominant
roan genes is almost always still born or dies
shortly after birth.
-Roan may occur in any base color - but the "blue"
effect comes only from Base Black.
Typically Grey and White pinto colored Gypsy
Horses are considered Blue and White by breeders
GUIDE TO COLOR
locus can be thought of as the gene that
determines if a horse is bay or black, although
other genes come into play. A horse that has at
least one dominant "A"
allele will be bay if it also possesses at least one
allele. A horse that is homozygous recessive for "a",
that is "aa",
will be black if it also possesses a "E"
horses are" E/‐,
a horse is homozygous for "e", it will have a sorrel
or chestnut base coat regardless of what genes it
carries at the A locus. Thus a chestnut horse may be
able to produce blacks if it carries an "a" allele
and is bred to another horse carrying the "a" allele
that also has an "E". If a person has a black horse
and wants to know if a breeding to a chestnut horse
will produce a black, the black horse needs to
tested for the E locus and the chestnut horse needs
to be tested for the A locus. A black horse that
tests homozygous for "a" must also be homozygous for
"E" to produce 100% blacks/bays/buckskins.
Like Cream Dilution, Champagne is a dominant
dilution gene, meaning that if the horse has even
one copy of the Champagne gene, it will express the
Champagne coloration. Unlike the Cream Dilution
gene, two copies of the Champagne gene has no more
effect than one copy on the horse's color. Horses
carrying the Champagne gene are born with blue eyes
that later darken to hazel or brown. In addition the
skin is pink and becomes mottled around the muzzle.
A Champagne gene on a black horse produces a Classic
Champagne, on a bay horse Amber Champagne, and on a
chestnut Gold Champagne. If the horse also carries a
Cream Dilution gene, the body color is further
diluted and it is referred to as a Classic Cream,
Amber Cream or Gold Cream Champagne. This mutation
was discovered by Deborah Cook, a student of Dr.
Ernest Bailey's, at the University of Kentucky.
WHY TEST: Since there is no way
to visually distinguish between a homozygous and
heterozygous Champagne horse, the test is valuable
to determine which horses will be 100% Champagne
producers (homozygotes). In addition it may be
difficult to distinguish horses homozygous for Cream
Dilution from those that carry the Champagne gene.
CREAM (Dilution) GENE
a dominant dilution gene that causes a reduction in
red pigment in the body hair and mane and tail hair.
It acts on any base color‐
therefore a sorrel horse that inherits one copy of
the Cr allele is palomino (ee, Cr/cr), a sorrel that
inherits a Cr from each parent is Cr/Cr and is a
cremello (ee, Cr/Cr). A bay horse that inherits a Cr
allele from one parent is a buckskin (E/‐,
Cr/cr), while one that is homozygous for Cr is a
perlino (ee, Cr/Cr). True black horses can mask the
presence of the Cr gene, so it is possible for a
black horse to produce palominos or buckskins. Cream
is a different gene than
which is also a dilution gene. In general, dun
horses have a dorsal stripe.
Owners of a black horse with a palomino or buckskin
parent may want to determine if the horse carries an
unexpressed Cr allele. Horses carrying the champagne
gene may be confused with horses carrying the Cr
test will verify if the horses indeed possess the Cr
allele. It will also determine if a dun or gray
horse may also possess a Cr allele.
October 2009 ‐
EXTENSION LOCUS (also referred
to as "red" gene test) ‐
locus controls expression of black pigment. This
is also a dominant gene, so that a bay or black
horse has at least one copy of the E allele. The
recessive form of this gene, "e"
restricts the distribution of the black pigment, and
a horse that is homozygous recessive or "ee"
is a chestnut or sorrel. A horse that is homozygous
for the dominant form or "EE"
will have black pigment and because it must pass a
"E" allele onto its foals, it can never produce a
chestnut or sorrel.
WHY TEST: In breeds where black
is valued, horses homozygous for E are important
because they cannot produce sorrels or chestnuts.
People breeding black or bay Paints/Pintos or
Friesian horses especially are concerned with the E
Gray is a dominant gene meaning that only one copy
is needed to be expressed. Therefore, a gray horse
must have at least one gray parent. Regardless of
the color of the horse when it is born, if it has
the gray gene, the coat will begin turning gray when
the foal coat is shed and the horse will get
progressively lighter throughout life. Ultimately a
gray horse is white or flea‐bitten
(white with small colored specks throughout the
WHY TEST: It may be hard to
determine in horses carrying dilute genes if they
also have the gray gene. In addition, if a horse has
two gray parents, it may be useful to know if the
horse is homozygous for the gray gene, in which case
all its offspring will inherit a gray gene.
Sabino is a Paint color pattern that is variably
expressed and can range from white stockings and a
blaze to white leg and face markings and extensive
white spreading up from the belly into the body
area. The mutation we detect is indicative of the
Sabino1 gene. Homozygous sabinos may have more
extensive white than heterozygous horses. There is
more than one sabino gene so that a horse that
appears to have the sabino pattern may test negative
for the Sabino1 gene. So far all horses that test
positive for Sabino1 have the sabino pattern.
WHY TEST: Horses that carry the
Sabino1 gene may produce white or near white horses
when bred to another Sabino1 carrier. The test
offers breeders information that will allow them to
selectively breed for the full expression (maximum)
Sabino1/Sabino1 horse will always pass a Sabino1
gene to its foals.
Silver dapple is a color also known as chocolate by
many breeders. Horses are a reddish to brownish
color with a flaxen/silver mane and tail. "Red
chocolates" refer to horses that carry the Silver
Dapple gene on a bay background. "Chocolates" refer
to horses that carry the Silver Dapple gene on a
black background. At least one copy of the E allele
(see Extension locus above) is required for the
Silver Dapple phenotype to be expressed. A chestnut
horse (ee) can carry the Silver Dapple gene but it
is not expressed. However when bred to a black or
bay horse a silver dapple phenotype can be produced.
The Silver Dapple gene (Z)
is dominant, therefore a horse only needs one copy
of the gene to be expressed.
WHY TEST: Horses that are
thought to have a purer light colored mane and tail
than heterozygotes (Zz).
A horse homozygous for
EE) will always produce silver dapple
(chocolate) offspring. Some breeders believe that ZZ
horses are at higher risk for an eye disorder known
as ASD (anterior segment dysgensis). Since chestnut
horses do not express Silver Dapple, the test
enables breeders to determine if a chestnut/sorrel
horse is a carrier for Z.
October 2009 ‐
is a spotted pattern generally characterized by
white areas on the body (that usually cross the
topline) interspersed with large areas of colored
hair, a dark face and four white legs. Tobiano is a
dominant gene, meaning that a foal can inherit
the gene from just one parent, and express the
tobiano pattern. Horses that have inherited a
Tobiano gene from BOTH parents are
and therefore will always pass on the Tobiano gene
to their foals.
Dr. Samantha Brooks at the
University of Kentucky discovered that a chromosomal
inversion is responsible for the tobiano spotting
pattern. This test is now the only tobiano test
performed at the University of Kentucky. Unlike
marker tests, the direct test for this inversion is
reliable across all breeds of horses tested to date.
WHY TEST: Breeders value horses that are
homozygous for Tobiano (TOB/TOB) because they will
always produce a spotted foal. A Tobiano horse that
is heterozygous (TOB/N) on the other hand, will only
produce a colored foal about 50% of the time.