Airedale Breeding in the 21st Century
Determining the Usefulness of Homozygosity Tools for Airedale Breeders
The above link has an article with results of our Airedale study with Dr. Angela Hughes Using Optimal Selection/MARS
Still Have Questions: Email: Angela Hughes, DVM/PhD at MARS Veterinary
***We have had an inquiry about the relationship
between AHF and MARS, Inc.
MARS Veterinary is a division of MARS, Inc. and is a research division with
goals to advance the understanding of canine health. The homozygosity study was conducted through Dr. Angela Hughes,
DVM, PhD, at the MARS Veterinary research division - and the DNA samples for the study were provided by volunteer breeders.
Other Methods to Determine Homozygosity in Breeds:
MHC Diversity Testing - Stay Tuned!
Genetic structure of the purebred domestic dog.
2004 May 21;304(5674):1160-4.
Parker HG, Kim LV, Sutter NB, Carlson S, Lorentzen TD, Malek TB, Johnson GS, DeFrance
HB, Ostrander EA, Kruglyak L.
We used molecular markers to study genetic
relationships in a diverse collection of 85 domestic dog breeds. Differences among breeds accounted for approximately 30%
of genetic variation. Microsatellite genotypes were used to correctly assign 99% of individual dogs to breeds. Phylogenetic
analysis separated several breeds with ancient origins from the remaining breeds with modern European origins. We identified
four genetic clusters, which predominantly contained breeds with similar geographic origin, morphology, or role in human activities.
These results provide a genetic classification of dog breeds and will aid studies of the genetics of phenotypic breed differences.
Three key definitions in the Homozygosity Study to consider:
Single nucleotide polymorphisms or genetic markers, where genetic variation has been found between different
Single nucleotide polymorphisms (SNPs) are DNA
sequence variations that occur when a single nucleotide (A, T, C, or G) in the genome sequence is changed. This occurs approximately
once every 100 to 300 bases. There are many techniques for SNP detection and genotyping, such as restriction fragment length
polymorphism PCR (RFLP-PCR), SSCP, allele specific hybridization, primer extension, allele specific oligonucleotide ligation,
Heterozygosity is when the dog
inherits different alleles from each parent.
is the opposite of heterozygosity and is when the dog inherits the same alleles from each parent.
homozygosity is determined for each dog and is the percentage of markers tested in the dog with the same allele (e.g. AA so
the dog inherited an A from the dam and an A from the sire).
How this is determined for the Optimal Selection
Analysis: For the average homozygosity in a breed, the level of homozygosity in each dog is averaged across all of the
dogs we have in our database for that breed (and the curve in the homozygosity graph shows the range of homozygosities observed
in the breed).
The goal behind study of homozygosity levels in any one breed:
Optimal Selection Genetic Breeding Analysis is a process that analyzes a dog's DNA on many key chromosomes. The
objective is to compare the chormosomes of potential breeding pairs, giving the breeder an opportunity to diversify the genetic
makeup of their puppies and reduce the risk of recessive medical conditions while still selecting for the physical and behavioral
traits that are important to them.
With this process, breeders can select a breeding pair
that will maximize the potential genetic heterozygosity (aligning different haplotypes on each chromosome). Studies
have shown that limiting heterozygosity (or increasing homozygosity) can cause decreased litter size and lead to greater health
risks, thus increasing individual heterozygosity can help with these issues.
Want more definitions
for genetic analysis terms? Click here.