The Institute of Canine Biology
  • HOME
  • Blog
  • Courses
    • COI BootCamp (FREE!)
    • Basic Population Genetics (FREE)
    • The Science of Canine Husbandry
    • Managing Genetics For the Future >
      • Syllabus - Managing Genetics for the Future
    • The Biology of Dogs (Open Reg )
    • DNA For Dog Breeders >
      • Syllabus - DNA for Dog Breeders
      • Open Reg - DNA For Dog Breeders
    • Understanding Hip & Elbow Dysplasia >
      • Open Reg - Understanding Hip & Elbow Dysplasia
    • Genetics of Behavior & Performance >
      • Syllabus - Genetics Behavior & Performance
      • Open Reg - Genetics of Behavior & Performance (Open Reg)
    • Strategies for Preservation Breeding >
      • Open Reg - Strategies for Preservation Breeding
    • Group Discounts
    • MORE FREE COURSES >
      • Quickie Genetics (Free!)
      • Heredity & Genetics (Free!)
      • Useful Genetics (Free!)
      • Basic Genetics Videos
  • Breed Preservation
    • Breed Status
    • Breeding for the future >
      • BFF Breed Groups
    • The "Elevator Pitch"
    • What's in the Gene Pool?
    • The Pox of Popular Sires
    • 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
  • 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)
    • Inbreeding Effects
    • Inbreeding (Gubbels)
    • Inbreeding (Dreger)
    • Lifespan
    • Litter size
    • Metabolic
    • 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)
  • Projects
    • How To Interpret Breed Analyses
    • 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
    • Breed outcrossing programs
  • Resources
    • Genetics Databases
    • Stud Books >
      • American Kennel Club stud books
      • Field Dog stud books
      • The Kennel Club (UK)
    • 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
  • Preventing Uterine Inertia

The easy way to understand the inheritance of recessive alleles

8/22/2018

 
By Carol Beuchat PhD
​

Most of the genetic disorders in dogs are caused by recessive mutations, a single broken allele. There are now tests for dozens of disorders that can detect whether a dog has inherited one or two copies of the broken version of an allele. With the DNA testing information, we can reduce or eliminate the risk of producing puppies that will be born with a disease caused by one of these recessive mutation.
We can predict the genes likely to be inherited by the puppies if we know the genotypes of both of the parents from DNA testing.

You have probably seen some busy-looking illustrated examples like the one to the right of the phenotypes to expect from the genotypes of the parents.

These are useful for illustration, but most people (well, speaking for myself) can't just memorize the illustration.

​In fact, there is an easier way to figure out the phenotypes to expect from particular genotypes and you don't have to memorize a thing. 
Picture
Picture
We can predict the genes likely to be inherited by the puppies if we know the genotypes of both of the parents from DNA testing. There have been some illustrated examples of the genotypes to expect from various combinations of clear (AA), carrier (Aa), and affected parents (aa). These are useful for illustration, but most people can't memorize the illustration. In fact, there is an easier way to figure out the phenotypes to expect from particular genotypes and you don't have to memorize a thing. 

​To do this, we can use something called a Punnett Square. Reginald Crundall Punnett was a British scientist that finished his degree in 1898 when things on the cutting edge of genetics were really getting hot. Experiments on Mendelian genetic inheritance of simple traits like size and flower color in sweet peas all the rage, and the concepts of recessive and dominant were throwing new light on the understanding of inheritance.


Punnet wanted to work out a simple way to predict the traits - the phenotypes - that would be inherited from parents. Knowing that each individual has paired alleles for a trait, one inherited from each parent, he came up with the Punnet square. Here's how it works.

Draw a square and divide it in half both ways to produce four compartments. Each compartment will represent a puppy (or a pea seedling, or whatever). Above each of the columns, note the genotype of the father for the gene in question, indicating the dominant allele with an upper case letter and the recessive version with lower case. On the left side, label the rows with the alleles present in the mother. In this example, the father is heterozygous for the B gene (Bb) and the mother is homozygous recessive (bb).
​
Picture

​

​Now, to see what we do next, click on this little alien that can't wait to show you the basics -
​
Picture

Knowing how to do a Punnett square, you can figure out the predicted proportions of phenotypes from combinations of parents with any genotype. So you don't need to memorize a busy chart like this one. Just sketch a square with four quadrants on the back of a napkin and work it out in seconds.

If fact, to convince yourself that you've got this, why don't you see if there are any errors in this one that has been circulating on Facebook! Remember to represent "clear" as AA (or whatever letter you want to use), "carrier" as Aa, and "affected" as homozygous recessive, or aa.
​

Just remember that these are probabilities. If you (OMG) were to have a litter of 100 puppies (or puppies from the matings of many parents with the same genotypes), you can expect to come close to the predictions from your Punnett square. But the alleles inherited by each puppy are random. As you know from flipping a coin, you shouldn't expect to get 5 heads and 5 tails from 10 tosses every time. But flipped 50 times it should be closer to 50:50, and 100 flips is likely to come close. 
Picture


The Punnett square works just as well for predictions of two traits at a time. Here's an example of a "dihybrid" cross involving two genes in guinea pigs, one for coat color and the other for coat length. The Punnett square makes it easy to map out all 16 possible combinations of inheritance in just a minute or two.
​
Picture


Have a go at checking the red, blue, and greed Ridgebacks and see if you get the same results for each pair of parents on the left. And below are some other examples you can play with. By the time you've worked through these, you'll be a pro!
Picture
Picture

If you enjoy learning about the genetics of dogs, check out ICB's online courses designed specifically for breeders and dog lovers.
​
ICB's next online course starts MONDAY, 27 August 2018

*** MANAGING GENETICS FOR THE FUTURE ***

Join us!

To learn more about the genetics of dogs, check out
ICB's online courses

***************************************

Visit our Facebook Groups

ICB Institute of Canine Biology
...the latest canine news and research

ICB Breeding for the Future
...the science of animal breeding


Comments are closed.

    Archives

    January 2025
    November 2022
    July 2022
    May 2022
    April 2022
    March 2022
    February 2022
    November 2021
    October 2021
    December 2020
    January 2020
    August 2019
    July 2019
    June 2019
    May 2019
    April 2019
    March 2019
    February 2019
    January 2019
    December 2018
    November 2018
    September 2018
    August 2018
    July 2018
    June 2018
    May 2018
    October 2017
    August 2017
    May 2017
    April 2017
    March 2017
    February 2017
    January 2017
    December 2016
    November 2016
    September 2016
    August 2016
    July 2016
    June 2016
    April 2016
    March 2016
    February 2016
    January 2016
    December 2015
    November 2015
    October 2015
    September 2015
    August 2015
    July 2015
    June 2015
    May 2015
    April 2015
    March 2015
    January 2015
    December 2014
    November 2014
    October 2014
    September 2014
    August 2014
    July 2014
    June 2014
    May 2014
    February 2014
    December 2013
    October 2013
    September 2013
    July 2013
    March 2013
    July 2012
    April 2012

    Categories

    All
    Behavior
    Border-collie
    Herding

Blog

News


About Us

Contact Us








Copyright © 2012-2017 Institute of Canine Biology
Picture
Picture