About
Merles and the Merle Gene
There
is no such thing as a
sable merle gene or a red or blue merle gene.
There
is only a merle gene.
Merle is an INCOMPLETE DOMINATE gene, which means this gene will
show
up in it's offspring. Merle is also a dilution gene,
that
is, it lightens
whatever the coat color would otherwise have been.
The
lightening is not spread
evenly over the coat, but leaves patches of undiluted color
scattered
over the dog's body. Also, the lightening seems to work primarily
on
the black pigment in the coat, so any tan on the face stays even.
Note
that "black" as
used here includes the brown color.
One
dose of the merle
gene on an otherwise black dog produces a blue merle - a more
or
less bluish gray dog dappled with black spots.
Tan
points - the tan spots
over the eyes, on the sides of the muzzle, on the legs and under the
tail
of a tricolor dog - will still be there in the merled tricolor.
If the
tan spots would not
be present in a black dog, tan will not be present in the merled black
either, and the dog will blue merle and white without tan.
One
dose of the merle gene
on an otherwise sable dog produces a sable merle.
Sable
merles are less predictable
in color than blue merles, and may range anywhere from an apparent
sable,
often with a pinkish or orange cast to its coat, to something
that
looks like a very rusty
blue merle. White markings remain on the merled dog, and may even be
slightly
more prominent.
Merle
acts on the dark
pigment in the iris of the eye just as it does on the coat, so merle
dogs
often have part or all of the eye blue.
(This does not affect their
vision,
though since it
happens to some extent in the retina as well it may make it harder to
diagnose
certain eye problems.)
Notice
what was said was
a
single dose of the merle gene. There are always two copies of a
gene,
alike or different, in any dog. If we call the merle
gene M
and the non-merle
gene m, any given dog can be
mm, Mm or MM.
The mm
dog is the normal,
full-colored tri, bi-color, or sable, or liver (red) in Australian
Shepherds.
The Mm Cocker is a blue merle, or brown merle, etc,depending on
what
color it would have been without the merling gene. An MM dog, often
called a double merle or a homozygous merle, will be mostly white
and
sometimes deaf or blind and often with other physical problems.
Some
MM puppies are born
completely without eyes.
On
average, over a large
number of litters, breeding merle to merle will produce one fourth full
colored dogs, one half merles and one fourth defective whites.
Breeding
merle to full color
will produce one half full color and one half merles, but no defective
whites. The merle to full color breeding, then, produces just as many
merles
as does the merle to merle breeding, and without the danger of
defective
puppies. The safe breeding for a merle, then, is to a non-merle
mate.
This
breeding should produce
all
healthy puppies, and about half will be merles.
To
breed in this way,
it is important to know which dogs are merles.
This
is one of the reasons
experienced breeders rarely breed blue merles to sables, or roans as
this
mating may produce sable merles or merles to the
inexperienced
breeder
to appear incorrectly as roans..
Sable
merles are no more
likely to have health problems than any other color.
Sometimes
you cannot tell
a sable is a merle unless you see it on the
tips of it's ears or the
eye or eyes are blue or blue flecked.,. The real argument against
sable merles is that they may be mistaken for normal sables.
If two
such sable merles were mated together, the resulting litter could
contain
defective whites.
The
sable gene can also
mask the merle, and as the dog ages it may be next to impossible to
tell
by looking that this IS a merle dog.
There
is one kind of breeding
that can produce all or almost all merles, and that is the breeding of
a tricolor or a bi-color to a double merle - but remember that the
double
merle in other breeds, has a high probability of being blind or
deaf.
Very
few breeders have been
lucky enough to get high quality homozygous merles that are not too
severely
affected to breed - but it definitely takes a lot of luck and really
top
quality blue merles to start with. Merle to merle breedings are only
for
the very experienced breeder who knows their lines and what they will
produce
- and it has probably produced more heartbreaks than good homozygous
merles,
even for them.
A blue
merle from black
to homozygous merle breeding is just as healthy as one from a more
normal
black to blue merle breeding.
Unless
you have done a
lot of merle breeding and really know what you are getting into, the
safe
rule is still that a merle should be bred only to a solid color
With
double merles, you
would actually have some normal colored hair, some diluted hair AND
some
double diluted hair. Each merle gene would dilute hairs in their
own pattern and that those patterns might or might not overlap.
Therefore
you can have 3 different colors of coat (normal coat, diluted coat and
double diluted "white") coat on a genetically SOLID dog! With
parti-colors,
the dogs could be almost or even entirely white since they already have
large areas of white.
Because
Cockers have a spotting
gene which can leave only small amounts of color on the dog, we can't
assume
that a merle with a lot of white is actually a double merle. A
normal,
single gene merle parti-color dog can have any amount of white that is
normal for a regular parti-color. We can have very open-marked
merle
Cockers and they are no more at risk to be defective than a normal
parti-color.
UPDATE!
Parts
of this next article
was borrowed from another site
This
article explains the
basic genetics about merling in easy to
understand
language. To
avoid confusion, the
dapple
was changed to merle
in the article.
http://www.dachshund.org/article_double_dapple.html
Explaining
double Merle and how it happens
It
is important to understand
that merle is NOT a color, it is a pattern
Merle
can be
compared to painting a room in your house. Say you paint the room
green.
Before
the paint is
allowed to dry, you dip a sponge in white paint and then dab the walls
with the sponge.
For
each spot that
the sponge touches, you will have a lighter green marbling affect that
results from the green and white paint blending together.
Merle
works in precisely
the same fashion. The merling can occur on any color.
A
merle black Cocker would
leave a black base with a gray marbling affect. A merle brown Cocker
would
result in a pinkish/tan or cream marbling affect.
Precisely
where the merling
chooses to occur is anyone's guess.
In one
litter of puppies,
you can have puppies that are merled from nose to tail or you can have
puppies with nothing more than a merle splotch on the top of the
head.
A well
merled puppy can
go on to produce lightly merled puppies, just as a lightly merled puppy
has an equal chance of producing heavily merled puppies.
There
is never rhyme nor
reason to how the merle gene chooses to act on a puppy. There are
responsible
breeders who have worked to understand the gene
and
how it works.
They've
also put much into
their program to produce healthy dogs, but, these breeders are far and
few between. IRRESPONSIBLE breeders have caused most of the
problems.
How
does it work?
Merle,
as
mentioned earlier, is a pattern. When two Cockers breed, they
both
contribute to each puppy's gene pool. Have you ever played the
card
game
"War"? In the card game both players are dealt an equal amount of
cards.
Player
'one' flips one card over and Player 'two' flips one card over.
The
player with the highest value card takes both cards and puts them in
their
pile.
The
game continues on until there are no cards left in either player's
hand.
You
can compare the genetic make-up of a puppy to a game of "War".
The
dam flips over one gene*, and then the sire flips over one gene.
The
'higher' valued gene (dominant) goes into the winner's pile.
The
'lower' valued gene (recessive) goes into the the loser's pile.
When
the game is over, the dominant pile is made up of the genes that
contribute
to the 'outside' of a puppy....those things that we see.
The
recessive pile is made up of the genes that contribute to the 'inside'
of the puppy...those things we can't see.
When
that puppy is old enough to breed, the dominant and recessive genes are
shuffled and a new game of 'War' begins.
In
the card game, you can sometimes have a tie, both players flip over the
same card of equal value.
This
can also happen with genes in a puppy. In the card game,
'War'
is declared and there is a 'showdown'. However dogs have never
been
known to be as competitive as humans are...dogs simply call it a draw.
It's
anyone's guess whose gene (the sire or dam) gets to go in the winner's
pile, but it is really irrelevant, since both genes are identical.
There
are thousands of genes involved in the make-up of a dog, from the shape
of his ears to the length of his tail. There are
approximately
300
known genes that contribute to coat color/pattern in dogs.
The
gene for merle is dominant over the gene for non merle.
As
an example, we'll say that the sire flips over the merle gene and the
dam
flips over the non merle gene. The two genes are compared and
the
merle gene goes into the winning pile...the part you will see on the
puppy.
The
non merle gene will go into the losing pile...the part you don't see on
the puppy.
Every
time a merle gene is passed on to a puppy, that puppy will be merle
because
a merle gene will always be dominant.
*Note:
For those
of you that are familiar with genetics,
I
wanted to mention that
many times the word 'Gene' is used in
place
of the proper term,
"Allele". I feel that describing alleles will only
confuse
the average viewer
and the point can be made by substituting the word 'gene'.
What
is a Double Merle?
If
both the sire and the dam of a puppy are merle, they both have an equal
chance of passing on their dominant merle gene to the puppy.
The
sire may flip over the merle gene, and the dam may flip over the non
merle
gene.
In
this case, the sire's merle gene would be dominant and that puppy would
be a merle.This confuses a lot of people. How can a merle dog
have
a non merle gene?
It
is easy to forget that every dog has a winning pile...what you see on
the
outside, and a losing pile...the recessive gene that is hidden.
If
each dog only
had
one gene to contribute, there would never be variety in the dogs. When
two dogs breed, the recessive genes are shuffled with the dominant genes
so
that they have a chance to manifest themselves. If the recessive
gene meets up with another recessive gene, it finally gets its chance
to
be in the winning pile.
However
if the recessive gene again meets a dominant gene, it has to wait
another
generation for the chance to dominate.
It
is also possible for
both the sire and the dam to flip over their non merle genes. If this
is
the case, it becomes a 'draw' and the puppy is not merle.
And
finally, it is possible for both the sire and dam to flip over their
merle
genes.
Again,
it is a draw, but something totally different happens.
We'll
say that the sire's merle gene gets to go in the winning pile.
The
puppy is now merle. But the dam also contributed a dominant
merle gene.
Her
gene says, "Whoa, wait a minute buddy!
What
do you think this is, the 19th century?
I
demand equal rights here! I want a chance to merle this puppy and
the 19th Amendment guarantees me that right!"
So
the dam's merle gene goes to work, after the sire's gene has already
made
the puppy merle. Since it's anybody's guess as to where
the
merle gene will hit (remember the sponge painting earlier?), the
outcome
will vary greatly. We'll assume, for ease
of understanding,
that
the sire merled the tail, and nothing more. The rest of the puppy was a
normal color and untouched by the merle.
The
dam's gene is mad at almost missing out on her chance, so she merles
the
entire body...from head to tail. The areas that the sire's merle
gene left untouched would now be merled by the dam's merle gene.
However,
the area that the sire's gene did merle (the tail) would be merled again.
Let's
go back to the paint. You finished the first coat of green and
then
finished sponging white paint over the wet green paint.
Now
dip the sponge in the white paint again. What do you think will
happen
when you start sponging the walls again? The areas that did not
get
touched by the first sponging, would now have the marbled look, but the
areas that were marbled the first time would now appear totally white.
This
is precisely what
happens when the merle gene is allowed to act twice on the same
area.
So,
What's Wrong with a Double Merle?
For
reasons unknown, the combination of two merle genes hitting the same
area
of the dog can be lethal. I have seen
double
merle puppies
born
with no eyes, and/or no ears. Blindness and/or deafness is
also caused by the double merle gene.
On
the other hand, a double merle can be born with no deformities at all.
There
are no facts or
figures available (that I have found) that tells us how many dogs like
this dog have been whelped. The double merle pattern is an
acceptable
pattern in some breeds that is recognized by AKC. In my
opinion,
if AKC continues to allow this pattern (which can only be achieved by
breeding
two merles together, so it is totally preventable) to be recognized,
then
serious studies should be done to look at the damage being done to the
dogs.
Why
Would Anyone Do This?
For
every deformed double
merle, there is a different excuse.
Here
are a few of those
'excuses' and a few solutions.
1.
Simple ignorance: Genetics are a complicated matter and many
breeders
won't even take the time to try to learn.
Solution:
TAKE THE TIME TO LEARN!
There
are two foundation
books on genetics.
Both
are
excellent books but both are out of print. Try your local
library!
"Genetics
of the Dog: Malcolm Willis"
"
Inheritance of Coat Color in Dog: Clarence Cook Little"
2.
Genetic
background unknown: Although the only way to get a double
merle is to breed two merles together, there are
many people that don't
know
they own a merle..since AKC has only allowed and has
ENCOURAGED
Cocker breeders to register their merle cockers as ROAN,
it can be very dangerous and heartbreaking for those who are uninformed
about merle.
a.
Some merled dogs often fade as they get
older. A dog that was poorly merled
at birth, and is sable or some other lighter color, will probably
not
be recognized as a merle later in life.
Solution:
Don't breed lighter colors or sables to merles.
If
you do, make sure you YOU UNDERSTAND genetics and the merle gene and
how
it works, AND BE ABSOLUTELY SURE to examine every puppy from head to
toe
at birth.
This
is when the merling is most noticeable.
Be
sure to mark a puppy as a merle, even if it has no hint of merle at
eight
weeks of age. CHECK the eyes!
If
the eye or eyes are
a lighter blue than normal puppy blue eyes, or have specks of blue in
them..be
safe and consider this dog a merle!
b.
Other colors of merles are often so lightly merled, they are not
marked as merle on their papers. In the case of Cockers, again,
many breeders
are
registering them as Roans, and every effort MUST be made to get ASC to
allow the merle pattern so AKC can register these dogs as merle.
Solution:
Again, be sure to record merles at
birth.
A
good sign of a merle (assuming one of the parents was a merle) is if a
puppy has any blue flecks in the eyes. The merle pattern can
color
the
iris
of the eyes, just as it covers the color of the coat. When the
merle
pattern hits the iris, it turns it blue, like that of a Siberian
Husky.
Since
the merle pattern is so sporadic, it can hit just a spot on the
eye,causing
a normal color eye with a tiny blue fleck. Always mark blue
eyed or
partial
blue eyed pups as merle if there is even the slightest chance that it
is
a merle.
Solution:
If you aren't sure if your dog is
double merle, look at the pedigree!
and
KNOW
THE BREEDER your dogs came from and ask them! Make sure the dog
is a merle and not called a roan .A
double
merle will always have a
merle
dam and a merle
sire. ONLY TWO MERLES can produce a
double merle.
The
ultimate test of
a double merle is to breed it to a SOLID colored dog.
If
ALL the puppies are
merle, your dog is a double merle!
GET
ON THE BANDWAGON AND CONVINCE THE AMERICAN
SPANIEL
CLUB TO GET THESE DOGS LISTED WITH AKC AS MERLES AND NOT ROANS OR
Some Other color without adding the merle pattern!!!!
3.
Greed:
If we go back to the genetics behind a double merle, you will remember
that a double merle results when two merles both contribute their merle
gene to one puppy. That puppy, if he goes on to breed, will have
two merle genes that will be shuffled and eventually dealt out into the
gene pool.
Since
the merle gene is an incomplete dominant, and the only thing that
puppy has is a merle gene, there is a 100% chance that every, single
puppy
that dog produces will be a merle.
In
other words, a double merle will ALWAYS produce merle puppies,
even
when bred to a normal color dog (black & tan, chocolate & tan,
etc.).
Since
merle puppies can command a higher price, due to it being "RARE", there
are breeders who purposely breed merle to merle, in hopes of getting a
double merle. That double merle can then be used to
produce
all merle puppies...all of his life.
It
is interesting to note, that even a dog which is totally blind and deaf
will NEVER produce a deaf or blind puppy (providing that he isn't bred
to another merle or carrying some other genetic defect that causes
deafness/blindness).
The
deafness/blindness seen in double merle is only a result of the two
merle
genes.
Solution:
There
is no solution for this sort of breeder.
Greed
is more powerful than compassion.
How
Can I Help?
The
double merle deformities
are not seen just in Cockers.
As
I mentioned earlier,
the pattern is seen in several other breeds of dogs.
Getting
the word our about irresponsible breeding of merles is important.
Many
of you are in large cities where you have the ability to get the word
out
about the possible dangers of double merle
breeding.
Many
of you attend dog shows regularly and can pass out literature (feel
free
to print this article) to people at the show.
Something
as simple as scanning the internet for breeders selling double merles
and
sending them the link to this article, can go a long way to educate a
lot
of people.
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