Page 102 - Aussie Magazine - 2024 Issue 3

Health
All cancers stem from genetic
mutations. Sometimes genes
that are supposed to signal
cell death at the appropriate
time fail to turn on. Or genes
important to cell division
get stuck in the “on” position
causing rapid production
of abnormal cells. Often it
isn’t a matter of a mutation
within a single gene: Entire
chunks of chromosomes
can become detached and
fasten themselves to other
chromosomes, disrupting
the proper function of
numerous genes.
Most cancerous mutations are
not inherited; they accumulate
throughout the body over
the course of a lifetime.
Exposure to certain chemicals,
radioactive substances or too
much sunlight might scramble
part of your dog’s DNA. As
the DNA is copied over and
over again throughout a dog’s
life, DNA transcription errors
can accumulate. Most of the
body’s cells are autosomal.
Only the germ cells produce
the sperm and eggs
necessary to reproduction.
If a cancer-causing mutation
occurs in germ cells, it can be
passed from one generation
to the next. Moby’s dam
also had mammary cancer,
a disease that has been
demonstrated to be heritable
in humans.
Cancer inheritance is rarely as
clear-cut as that of traits like
coat color. Mutations linked to
cancer often only predispose
a dog to develop the disease.
Whether it remains healthy
or not will depend on what
102 | A Worldwide Magazine for the Aussie • Issue 3/2024
other risky mutations, or sets
of mutations, it has or will
acquire as it goes through life.
Or the balance can be tipped by
something in the environment.
A dog breeder can only do
a limited amount to control
exposure of her puppies to
environmental carcinogens
and nothing at all to prevent
DNA copying errors. She can
do something about inherited
predisposition, but only if she
knows what cancers her breed
and bloodlines are prone to.
I FIRST BECAME
CONCERNED
ABOUT THE
HERITABILITY
OF CANCER IN
AUSTRALIAN
SHEPHERDS IN
THE LATE 1990s.
At that time I was assisting of the American West. Since
the late Dr. John Armstrong, that time, breed type has
a geneticist at the University been refined and standardized
of Ottawa, with his canine through linebreeding. This
longevity study. He gathered is a normal and necessary
data on several breeds, step to breed development.
including the Aussie. He However, it is not without
told me that cancer was the risks. In the process certain
most common cause of non- individuals, usually males, will
accidental death, which is a become disproportionately
normal finding in dogs. But he represented in the breed
went on to say than among gene pool. These will be
more recent dogs cancer dogs that not only exhibited
appeared to be happening with highly desired traits, but
increasing frequency in dogs reproduced them consistently.
that were not old. But along with all those
desirable genes, some that
Our breed developed mostly in are far less desirable will have
the early-to-mid-20th century hitched a ride into subsequent
from indigenous ranch dogs generations.