2017 June July

Q&A
Do These Genes Fit?
I just got my DNA color test certificate
back from Paw Print Genetics for my
red tri girl. For merle it says “likely nonmerle
(cryptic merle carrier).” From the
interpretation, should she NOT be bred
to a merle?
Thank you for your question. Because
your results contradict earlier knowledge
about cryptic merles I decided to do some
investigating to see if what is known about
the various versions of merle has changed
and got in touch with Paw Print.
Before the merle gene was found,
cryptic merles were thought to be only an
extreme variation in merle phenotype (what
the dog looks like), sort of the opposite of
a merle with only a very few dark spots
(black or liver) and the rest all diluted
(blue or light red). People thought if you
bred them to merles you would get double
merles.
When the merle gene was found, a
“cryptic allele” was identified. It was felt
that it fell in dominance between the merle
version of the gene and the non-merle
gene. If a cryptic were bred to a non-merle
it would produce cryptic merles and with
a merle it would produce merles and
cryptics. Cryptic merles typically have one
or a few small merle areas. However, since
you can’t see what color coat would have
been anywhere there are white markings
it was assumed that come cryptics looked
non-merle because their merle spots were
obscured by white trim. Your girl is an
example of this.
I contacted Paw Prints’ Associate
Medical Director, Dr. Casey Carl, and
learned that what was previously felt to be
the case is incorrect. The merle mutation is
a bit of inserted DNA called a SINE (short
interspersed nucleotide element) that can
change in length from one generation to
the next. This accounts for why the merle
Send your questions to:
C.A. Sharp
1338 Trouville Ave.
Grover Beach, CA 93433
ph. 805-473-0078
e-mail: 51ca@ashgi.org
pattern can be so variable. Even within a
single litter, some pups have smaller or
fewer dark spots and others have many or
great big ones: The longer the insertion, the
more merle you see on the dog. When the
length of the insertion falls below a certain
threshold, the dog is likely to have no merle
areas or only one or more very small ones.
Test results for such dogs will indicate they
are cryptic merles (or carry, depending on
the other copy of the gene). Paw Prints uses
M cr to indicate the cryptic version of merle;
other labs may use something different.
If you have a cryptic merle and breed
it to a non-merle, the puppies may be nonmerle
or have a limited amount of merleing
on them. How limited will depend on how
long the insertion is in each puppy’s merle
gene. If you breed two cryptics together you
may have puppies with varying amounts of
merle but probably not a whole lot based on
the limited amount of litter data on cryptic/
cryptic crosses. A cross between a merle
and a cryptic usually produces puppies of
each type. However, Dr. Carl said there is
about a 3% chance of a cryptic to merle
breeding producing double merles. So, it
can happen but does not happen very often.
You need to decide wither or not you are
comfortable with that level of risk when
considering breeding your cryptic merle
to a merle. If you aren’t, then don’t do it.
This case is an excellent example of
how science is not static. Current knowledge
is open to question and whenever there is
sufficient evidence that an assumption
based on prior knowledge was incorrect,
the accepted knowledge will change. Here
are two examples that occurred during
my lifetime (I’m old, but not ancient.):
Scientists once thought that continents did
not drift nor that humans could survive the
levels of radiation in space for even a little
while. Today we know both these onceaccepted
assumptions are wrong.
I have a tri girl with blue eyes. Someone
told me this means she is a cryptic merle.
Is it OK to breed her to a merle dog? Do
I need to have her DNA tested for this?
Blue eyes do not mean a tri is a cryptic
merle. There is a gene for blue eyes that
can cause them in any color dog. Cryptic
merles typically have one or more small
merle spots somewhere on the coat but
sometimes they don’t. If you are worried
about it, do the test mentioned above and
you will know for sure whether your dog
is cryptic.
So a friend of mine wanted to breed her
girl to my dog but I found out her girl
has thrown bad bites. My boy has a good
bite, but his dam has several littermates
with bad bites. Probably not a good cross,
I’m guessing. What is the “long term”
inheritance for that? Is it recessive?
Dominant? How long to breed away from
it?? Is this cross not a good idea?
Not if what you want to do is avoid
bad bites.
The inheritance of bites is complex
– possibly multiple genes and. And, since
it is a developmental defect, there may
be regulatory DNA involved, something
scientists are only beginning to get puzzled
out. With this sort of trait you may think
you’re beyond it because you’ve eliminated
some crucial part of the genetic mix only
to get it again when you happen to make a
cross that brings whatever you eliminated
back in.
AUSSIE TIMES May-June 2017 91