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A DNA test for Multidrug Resistance (MDR1) in Collies.
What is MDR1?
A DNA test for MDR1
"Dangerous drugs" for oversensitive dogs
Breeds at risk
Breeding policy
Of the utmost importance is the control of hereditary disorders in breeding
programs. Thus, in order to reduce the frequency or eliminate altogether a
genetic defect, the further spread of the mutant gene has to be prevented in
a family or entire breed. When we find an inherited disorder in our population
(in our breed), especially when the frequency of affected animals is quite high,
most of us would want to exclude all animals that carry the defective allele on
the shortest possible term.
That's not always the best thing to do. Eliminating all affected animals and
all carriers from our breeding programs in just one generation may result in
a tremendous reduction of the breed's gene pool, thus causing an enormous
increase of the level of inbreeding. As a consequence problems with the
vitality of the population will increase and we probably will see outbreaks
of other genetic disorders.
Each dog with the defective allele has many good and important genes that may
be worthwhile to preserve in the population. Selection programs should be
carried out slowly and carefully, taking a sufficient number of generations
to prevent overselection. That is where the breeders' organizations should
take their responsibility towards their breeds. With the availability of a
DNA test for disorders like the MDR1 defect, selection programs can
be extended to the number of generations needed to make sure that no harm is
done to the breed's gene pool.
Carriers can still be bred to clear dogs, thus avoiding the birth of highly
susceptible affecteds. Pups that will be used for breeding the next generation
can themselves be DNA tested to determine whether they are clear or carrier.
Of course, where the MDR1 defect is involved, extra attention should be paid to
the heterozygous animals (the carriers, MDR1/mdr1-1Δ). There have
been reports of a (limited) susceptibility for certain drugs. So whenever
medication is required, checking the latest updates of the listings of
"dangerous drugs" is advisable.
Testing for MDR1
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