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