Genetics and dog breeding Flashcards
Most Popular Dog Breeds
Labrador Retrievers (29 years in a row) – data from the American Kennel Club (AKC) so this means ONLY registered breeds and ignores popularity of designer breeds
-then german shepherd, then golden retriever…
can mixed breeds register with AKC?
AKC has realized they were losing a huge clientele and you can now register your mutt (or designer breed or whatever) through the AKC Canine PartnersTM Program
This allows “mutts” to participate in sporting events with their owners
Reasons for Genetic Testing
Paternity
Disease testing
> Carrier (recessive traits)
> Affected
> Clear
Trait testing, eg. coat colour testing eg. does this black Lab carry chocolate or yellow? (formerly pedigree analysis)
peternity testing methods
DNA“Fingerprinting”
BloodTyping
AKC requirements for Frequently Used Sires (FUS), frozen semen, etc.
types of DNA tests for paternity
Usemarkers
The AKC used 10 now 14 with gender verification too (MMI)
Other labs will perform this too
Ask CKC about which lab results they will accept
AKC DNA Data bank breadth
As of Dec., 2012 the AKC collected over 653,000 DNA profiles from 228 breeds
In 2017, the top 11 breeds AKC DNA Profiled
> Labrador Retriever; Yorkshire Terrier; German Shepherd Dog; Dachshund; Poodle; Chihuahua; Golden Retriever; Shih Tzu; Pomeranian; Beagle
> These are not the same as the most popular breed list
AKC DNA Profile Program; how does it work and how extensive is it
>709,000 samples have been submitted
voluntary basis and/or to satisfy AKC DNA requirements.
Frequently Used Sires (FUS) Requirement
>45% of pups registered are from FUS
Some argue this is the biggest problem in purebred dogs
What is the AKC multiple-sured litters requirement?
previously, if your bitch had been bred to more than one stud dog, AKC would refuse to register the litter
-often, owners wouldnt know about multiple sires
-test all puppies to determine sires
- now 14 markers and XX vs XY, no ‘unidentifiables’
what is the AKC compliance audit program?
-AKC may show up and ask you for DNA samples from your dogs
-when program started, 11% of ‘purebreds’ were not actually
-identifies puppy parentage
-this program only in USA, not canada
>Expect at least 10% of puppies in Canada have wrongly identified parents
how many inherited diseases described in dogs? usually caused by what kind of mutation?
350 to 600 inherited diseases described in dogs
precise mode of inheritance known in ~half
-85% caused by a single gene mutation (monogenic disorders)
- 70% single recessive
- 10% polygenic (eg. hip dysplasia)
what can the canine health information center tell you?
CHIC site allows you to search by breed or disease - tells you what a breed should be tested for at minimum
>good for client info before they get a dog
>helps with breeding decisions
>open to public
Influence of Single Sire on Genetic Diseases: common problem in doberman
Doberman Pinschers and von Willebrand’s Disease
how has DNA testing allowed us to decreased affected animals
DNA testing has decreased affected animals by breeding clears to carriers
1997: 30% affected/51% carriers/19% clear 2008: 19% affected/46% carriers/35% clear
Methods of Genetic Testing
Phenotypic tests, eg. CAER (Companion Animal Eye Registry), PennHip, OFA hips, elbows, shoulder, BAER hearing test, etc.
Metabolic screening eg. urine in MPS VI
DNA (really only one to test for those diseases that are not apparent at a
young age and best for “carriers”)
Parental tests with above
classic example of a partially hereditary genetic condition
hip dysplasia
difference between a horizontal and vertical pedigree
-horizontal only looks at parents, grandparents
- vertical looks at siblings as well, for all generations
> vertical tells you a lot more about what that animal may be carrying
issue is that we rarely have this much information about siblings
OFA reccomendations for fair hips; when is a fair dig a good breeding prospect
Fair hips may be within normal limits
eg. Fair hips with a strong hip background and >75% of siblings normal is a good breeding prospect
eg. Excellent hips, but with a weak family background and <75% of its siblings normal is a poor breeding prospect
OFA’s Recommended Breeding Principles for hip dysplasia
- Breed normals to normals
- Breed normals with normal ancestry
- Breed normals from litters (brothers/sisters) with a low incidence of HD
- Select a sire that produces a low incidence of HD
- Replace dogs with dogs that are better than the breed average
how are hereditary diseases of purebred dogs tracked?
Every breed has a list of diseases, constantly updated
Breeders ‘know’ what these are and often what lines have them
Every breed has internet sites with information
World Small Animal Veterinary Association (WSAVA); what info does it give you?
Web site searchable by breed, disease or laboratory
>Can be used to find nearest lab or best lab for testing for breed and also names, when known, the gene being tested
Samples for DNA Testing
Whole blood in EDTA (lavender top)
Cheek (buccal) swab with brush
Dried blood on filter paper
what is a wisdom panel?
mixed breed analysis by Mars Veterinary
>tells you what breeds are in your dog
- only check EIC and MDR1 disease genes
-cheek swabs
what test is available for mutt health?
Royal canin genetic health analysis (blood)
- performed by Mars
-
limitatins of mutt genetic testing? uses and issues?
Can’t “verify” it’s a purebred since can’t test for EVERY breed, but can be more sure
Various claims, most ~90% accuracy
Prices have come down, all use cheek swabs now
Only two companies as there was an issue of patents
Those performing both breed and DNA use blood rather than cheek swabs
use of fecal DNA detection for dogs
-enforce stoop and poop laws
should designer breeders (hybrid) do generic testing? do they often do this?
Many do a lot of genetic testing of parents
Web sites of those producing designer breeds RARELY say
they do genetic testing
Counsel clients to do their homework before purchasing any dog
MUST test parents for common genetic diseases PRIOR to breeding
Use clear parents differently from carrier
Use common sense, for example, bad heart worse than missing teeth!
Types of DNA Tests for Disease
Single gene testing
>Clear or Carrier or Affected
ie. Rare false results unless > 1 gene causing same disease (PRA in Chinese Crested)
Linked-marker gene(s) testing
>A or B or C based on frequency of the marker in the population not linked and % recombination reported at the lab,
ie. Subject to Major interpretation!!
Counseling Considerations for DNA test and conditions
Type of DNA test used
Dominant or recessive trait or X-linked
Genetic pool for the breed
Certainty of a genetic basis for the congenital/adult disease/condition
Severity of disease/condition to health/quality of life of the individual
>eg. cryptorchidism vs PRA vs lysosomal storage disease
most common veterinary species with genetic defects? what types?
canine
Musculoskeletal most common followed by organs of special sense
is a congenital defect always genetic?
Congenital defects are often genetic, BUT
Possible Teratogens: medicines, environmental exposures, vaccines, radiation, plants, nutrition, viruses, circulatory disturbance, mechanical factors, aged gametes, aged parents, and UNKNOWN
Karyotype abnormality – maybe hereditary (eg. Robertsonian Translocation) or aged gametes and parents
what is the litter effect for generic disorders?
Rarely do all fetuses respond to the same degree
Fetal death, infertility, stillbirth, mummification, congenital defects, apparently normal neonates dying shortly after birth, totally normal puppies
how do we approach a diagnosis for congenital disorders?
History (as available) of similar defects in related dogs
>Problem with teasing out environment from genetics in a “kennel”
Lists of common defects by breed are available
>Cleft palates in Bulldogs and other brachycephalic breeds
Compare defect with reports in other species, eg. humans, cattle
>Need to do complete gross and perhaps further post mortem or workup
>Karyotype analysis
>Internet
History during pregnancy eg. medicines, exposure to teratogens
When exposed eg. palate closes about 5 weeks of gestation
Exposure to other dogs eg. returning from shows or new arrivals
what contributes to possible teratogenicity of drugs?
Properties of the drug, eg. metabolism, lipid solubility Concentration and duration of drug in dam and any
metabolism
Access to fetuses
Stage of development at exposure
Fetal metabolism of drug
Individual susceptibility
“Litter effect” – fetuses will not all respond the same- death, resorption, mummification, congenital defects, stillbirth, normal
