The Institute of Canine Biology
  • HOME
  • Blog
  • Breed Preservation
    • Breeding for the future >
      • BFF Breed Groups
    • Breed Status
    • The "Elevator Pitch"
    • What's in the Gene Pool?
    • What population genetics can tell us about a breed
    • What population genetics can tell you...Tollers & Heelers
    • How to use kinship data
    • Using EBVs to breed better dogs >
      • How population size affects inbreeding
      • EBV Examples
    • How to read a dendrogram
    • Global Pedigree Project >
      • The Database
    • Finding the genes without DNA
    • How to read a heat map
  • Courses
    • COI BootCamp (FREE!)
    • Basic Population Genetics (FREE)
    • Genetic rescue: the genetics of cross breeding (NEW!)
    • The Biology of Dogs (Open Reg )
    • Managing Genetics For the Future >
      • Managing Genetics For the Future Open Reg (Open Reg) >
        • Syllabus - Managing Genetics for the Future
    • Genetics of Behavior & Performance (Open Reg)
    • Strategies for Preservation Breeding (Open Reg)
    • DNA For Dog Breeders (May2025) >
      • DNA For Dog Breeders (Open Reg)
    • Understanding Hip & Elbow Dysplasia (Open Reg) >
      • MORE FREE COURSES >
        • Quickie Genetics (Free!)
        • Group Discounts
        • Useful Genetics (Free!)
        • Strategies for Preservation Breeding (Sept 2023) >
          • Heredity & Genetics (Free!)
        • Basic Genetics Videos
  • Health Data
    • Bloat (Purdue Study)
    • Body Condition Score >
      • % Dysplastic vs BCS
    • Breed Comparions
    • Cancer
    • Cardiac
    • Cataracts
    • Caesareans
    • Deafness
    • Degenerative Myelopathy
    • Elbow Dysplasia
    • Epilepsy
    • Genetic Diversity
    • Genetic Diversity (MyDogDNA)
    • Hip Dysplasia >
      • Hip Dysplasia (Hou et al 2013)
    • Metabolic
    • Inbreeding Effects
    • Inbreeding (Gubbels)
    • Inbreeding (Dreger)
    • Lifespan
    • Litter size
    • mtDNA
    • Orthopedic
    • Mode of Inheritance
    • Patella Luxation
    • Thyroid
    • Portosystemic shunt
    • Purebred vs Mixed (UC Davis)
    • Purebred vs Mixed Breed (Bonnett)
    • Spay & Neuter Effects
    • Calboli et al 2008
    • Hodgman (1963)
    • Scott & Fuller (1965)
    • Stockard: Purebred crosses
    • Summers (2011)
  • Resources
    • Stud Books >
      • American Kennel Club stud books
      • Field Dog stud books
      • The Kennel Club (UK)
    • Genetics Databases
    • Learn
    • Videos about dog genetics
    • The Amazing Things Dogs Do! (videos) >
      • Livestock Management
      • Livestock guarding
      • Transportation, exploration, racing
      • Conservation & wildlife management
      • Detection Dogs
      • Medicine & Research
      • Entertainment
      • AKC/CHF Podcasts
    • Read & Watch
    • Bookshelf
  • Projects
    • How To Interpret Breed Analyses
    • Ilska et al 2025 Figures >
      • # of dogs whole pedigree (Ilska)
      • Percent of Dogs Bred (LReg 2005-15)
      • % Males Bred
      • Imported Sires
      • Proportional Population Growth
    • Afghan Hound
    • More details about the Toller study
    • Belgian Tervuren >
      • Belgian Terv p2
      • Belgians- why population size matters
    • Bernese Mountain Dog
    • Boxer
    • Brussels Griffon
    • Bullmastiff
    • Canaan Dog >
      • Canaan analyses
    • Cesky Terrier >
      • Cesky genetic history
    • Chinook
    • Curly-coated Retriever
    • Doberman
    • Entelbucher Mountain Dog
    • Flatcoat Retriever
    • French Bulldog
    • German Shorthair
    • Golden Retriever >
      • Golden Retriever Pedigree Charts
    • Irish Water Spaniel >
      • IWS (6 Nov 17)
    • Labrador Retriever
    • Manchester Terrier
    • Mongolian Bankhar >
      • Research Updates
      • Bankhar 1
    • Norwegian Lundehund
    • Plummer Terrier
    • Otterhound
    • Portuguese Water Dog >
      • Portuguese Water Dog (pt 2)
    • Ridgeback
    • Schipperke
    • Standard Poodle >
      • The Problem With Poodles
      • 3poodle pedigree charts
      • 3Poodle Wycliff dogs
      • Poodle Genetics
    • Tibetan Spaniel
    • Tibetan Mastiff
    • West Highland White Terrier
    • Whippet
    • Wirehaired Pointing Griffons
    • UK KC Graphs >
      • UK KC Breed Status
      • UK Groups
      • KC Gundogs
      • KC Hounds
      • KC Terriers >
        • Terriers (select breeds)
      • KC Pastoral
      • KC Toys
      • KC Working
      • KC Utility
      • Australian KC
  • Genetics
    • Genetic Status of UK KC Breeds (2015)
    • Heterozygosity (DNA) >
      • Heterozygosity vs COI
      • Heterozygosity
      • High and Low Heterozygosity
      • Heterozygosity Countries
      • Heterozygosity by Breed
      • EU Breed Skull Restrictions
    • Mortality (Lewis et al 2018)

What's in the Gene Pool?

The founding of the breed - the Gene Pool

Picture
Let's pretend these 11 dogs are the "founders" of your breed - they are the first dogs entered into the studbook.  All subsequent members of the breed are descended from these dogs only.  The breed has a closed gene pool.

All of the genetic variability that will ever exist in your new breed is present in these dogs.  Mutations probably won't add new, useful genetic variation because most mutations are detrimental.  If the mutated gene is dominant and detrimental, it will likely be weeded out very quickly.  If the mutation is recessive, it is not expressed unless an animal is homozygous for the allele by inheriting a copy from each of its parents.  In the heterozygote condition, a mutated recessive allele can lurk in the genome for generations without ever causing a problem.  So, unless additional "founders" are added to the population at a later date, all of the genes you will ever have to work with in your breeding program are present in these dogs.

In each of these dogs there are at least a few (and perhaps many) recessive genes that could cause genetic disorders.  But these disorders will only expressed if a dog is homozygous for the disease allele - it must have TWO copies, one from each parent.  As long as the disease genes are rare in the population, very few animals will ever display the illness.




Can the gene pool get bigger? (No!)

Picture
Okay, starting with your 11 founder dogs, let's let them reproduce.  To keep it simple, we will let them produce only identical copies of themselves - clones.  

Now we have 27 dogs, all of which are exact copies of one of the founders.  What has happened to the size of the gene pool?

Nothing.

You now have more dogs, and you now have more copies of the genes found in the dogs that had more offspring, like that busy gray dog with the red tongue.  So, the frequency of particular alleles is different in this population than in the founders, but the number of different alleles in the population is exactly the same.  (We're ignoring the possibility of a mutation for now.)

What if the dogs reproduce normally instead of producing clones?  In sexual reproduction, each puppy receives one set of genes from each parent.  And, each puppy receives a different mix of parental genes, so each one is a bit different.  Also, each parent dog has a different number of offspring and might mate multiple times with different dogs.  So the frequency of the various alleles in the population could be very different in this new population than in the founders.

But again, even though there are now more dogs in the population, the gene pool does not get bigger.

In fact, it doesn't matter how large this breed gets - it might someday grow to thousands of dogs - but as long as the stud book is closed, the gene pool will never be larger than it was when the breed is founded.


Can the gene pool get smaller?  (Yes!)

Picture
The gene pool of a closed breed can never get bigger.  But it can get smaller.

What if dogs with black ears were less fertile, or had higher puppy mortality, or had some other biological problem?  The frequency in the population of the genes causing the black ears would be reduced by natural selection - black-eared dogs would contribute fewer copies of their genes to the next generation. Eventually, by genetic drift (chance) or natural selection, the genes in black-eared dogs would become rarer and rarer, and might eventually be eliminated from the population entirely.

What if breeders didn't like black ears, so all the puppies with black ears were spayed or neutered and sent to pet homes?  Those alleles will become less frequent in the population, and they might be eliminated completely because of artificial selection courtesy of the breeder.

The gene pool gets smaller when genes are completely eliminated from the population.  It is unlikely that a gene will be restored by chance mutation, and the only other way it can be restored is if an animal is introduced into the breeding population that carries that gene and who reproduces successfully.

In purebred dogs, when the stud book is closed, no new alleles can be introduced into the breed.  The loss of an allele is permanent and reduces the heterozygosity in the genome for that gene.






Blog

News


About Us

Contact Us








Copyright © 2012-2017 Institute of Canine Biology
Picture
Picture