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| Last updated 12 October 2011 |
| Color Genetics |
Ok... here's my take on beginner color genetics!
A dog's phenotype describes the way it appears physically. A dog's genotype describes the genetics
behind the physical characteristics. It might help to remember this as PHenotype = PHysical and
GENotype = GENes.
One can easily ascertain a dog's phenotype simply by looking at it but the genotype takes a bit more
digging in some cases. You can deduce it with varying degrees of accuracy by looking at anecdotal
breeding information. The more definitive option is to have a dog tested through the services of
companies like Vetgen in Ann Arbor, MI. The test requires a cheek swab as is commonly used for
standard DNA testing and results are usually available in a week or so.
This topic relates to Portuguese pointers primarily due to the fact that there is a simple recessive gene
for brown pigmentation of the skin usually accompanied by a light eye color still lurking in many - if not
most! - pedigrees. (We aren't talking about coat color here as that is a whole different set of genes and
in modern day Portuguese pointers, only yellow coats exist.) This coloring is referred to as "lemon" in
[English] pointers. If you've perused our C Litter puppy pictures, you've seen the results with Chamusca
who bears the brown pigmentation. Here is the very basic science behind how two yellow-coated dogs
with black skin pigmented, known as "orange" in [English] pointers, when bred together, can produce
brown-pigmented offspring.
Color genes can be represented as pairs of letters. The letter B will represent black skin pigment and b
means brown skin pigment. Whenever a B is present in the pair, as black is dominant, the result will be
a dog with black skin pigmentation, regardless of whether the other letter is B or b. It's only when the
pairing consists of bb that the brown skin pigment will be expressed.
In the case of our C Litter which produced a puppy with brown skin pigment (a brown nose, lips and eye
rims), Chamusca, we know her genotype must be bb. As each parent contributes one of the genes to
the pair, we therefore know that both Haizen and Rena must carry the b gene. Since they both have
black skin, we can easily deduce that the other gene in their pairs must be B and, therefore, their
genotypes are be Bb.
With this combination (Bb x Bb), the following distribution should result:
BB Bb or bB bb
25% 50% 25%
Based on what you know about the effect of B on the physical color, you'll see that theoretically 75% of
the puppies should be black (BB, Bb or bB). We have since had Constancia and Cadaval tested and
they are Bb and BB, respectively. If there had been a fourth puppy and the odds had played out true,
that puppy would have been Bb and black as well. But probabilities being what they are, it's difficult in
this instance to determine what you will get and Chamusca could have as easily been BB or Bb! This
is why anecdotally determining genotype of black-pigmented dogs used for breeding can be difficult if
the tell-tale brownie isn't produced!
As an interesting note, Cadaval being BB can never produce a brown pup, regardless of which
genotype she is bred to, including a brown-pigmented dog. Likewise, if Chamusca as a bb were bred to
a BB dog, she would not produce brown pups, either.
And if you're ready to advance your understanding of genetics in Portuguese pointers, there's the issue
of long hairs and short hairs! Fortunately the genetics behind coat length appear pretty straightforward
as well with the long hair being a simple recessive, meaning both parents have to carry carry a copy of
the long hair gene to produce long hair pups. And, there's also simple DNA test also utilizing a cheek
swab.
A dog's phenotype describes the way it appears physically. A dog's genotype describes the genetics
behind the physical characteristics. It might help to remember this as PHenotype = PHysical and
GENotype = GENes.
One can easily ascertain a dog's phenotype simply by looking at it but the genotype takes a bit more
digging in some cases. You can deduce it with varying degrees of accuracy by looking at anecdotal
breeding information. The more definitive option is to have a dog tested through the services of
companies like Vetgen in Ann Arbor, MI. The test requires a cheek swab as is commonly used for
standard DNA testing and results are usually available in a week or so.
This topic relates to Portuguese pointers primarily due to the fact that there is a simple recessive gene
for brown pigmentation of the skin usually accompanied by a light eye color still lurking in many - if not
most! - pedigrees. (We aren't talking about coat color here as that is a whole different set of genes and
in modern day Portuguese pointers, only yellow coats exist.) This coloring is referred to as "lemon" in
[English] pointers. If you've perused our C Litter puppy pictures, you've seen the results with Chamusca
who bears the brown pigmentation. Here is the very basic science behind how two yellow-coated dogs
with black skin pigmented, known as "orange" in [English] pointers, when bred together, can produce
brown-pigmented offspring.
Color genes can be represented as pairs of letters. The letter B will represent black skin pigment and b
means brown skin pigment. Whenever a B is present in the pair, as black is dominant, the result will be
a dog with black skin pigmentation, regardless of whether the other letter is B or b. It's only when the
pairing consists of bb that the brown skin pigment will be expressed.
In the case of our C Litter which produced a puppy with brown skin pigment (a brown nose, lips and eye
rims), Chamusca, we know her genotype must be bb. As each parent contributes one of the genes to
the pair, we therefore know that both Haizen and Rena must carry the b gene. Since they both have
black skin, we can easily deduce that the other gene in their pairs must be B and, therefore, their
genotypes are be Bb.
With this combination (Bb x Bb), the following distribution should result:
BB Bb or bB bb
25% 50% 25%
Based on what you know about the effect of B on the physical color, you'll see that theoretically 75% of
the puppies should be black (BB, Bb or bB). We have since had Constancia and Cadaval tested and
they are Bb and BB, respectively. If there had been a fourth puppy and the odds had played out true,
that puppy would have been Bb and black as well. But probabilities being what they are, it's difficult in
this instance to determine what you will get and Chamusca could have as easily been BB or Bb! This
is why anecdotally determining genotype of black-pigmented dogs used for breeding can be difficult if
the tell-tale brownie isn't produced!
As an interesting note, Cadaval being BB can never produce a brown pup, regardless of which
genotype she is bred to, including a brown-pigmented dog. Likewise, if Chamusca as a bb were bred to
a BB dog, she would not produce brown pups, either.
And if you're ready to advance your understanding of genetics in Portuguese pointers, there's the issue
of long hairs and short hairs! Fortunately the genetics behind coat length appear pretty straightforward
as well with the long hair being a simple recessive, meaning both parents have to carry carry a copy of
the long hair gene to produce long hair pups. And, there's also simple DNA test also utilizing a cheek
swab.