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Highlights of a seminar
Dog Breeder as Scientists    Aug 4,2006

Mellissa L. Cox, PhD (Thesis in Genetic Lab, Texas – kidney disease)
WSCC National Show

 

Mellissa proposes that a breeders need to view their breeding programs as a scientist.  We must follow the same 7 steps scientists do when they conduct their experiments, come up with new theories, etc. 

Tools for breeding program

1). Education. A breeder should understand basic principles of genetics and how to objectively evaluate a particular dog for breeding purposes.
2). Observation – educated evaluation of pedigree, health tests, working ability, temperament, structure, movement, etc.
3). Hypothesis – the puppies of Dog A x Dog B will better the breed.
4). Experimentation – Conducting the actual breeding, raising puppies, selecting new owners, placing pups to the right homes.
5). Data Collection.  Track your puppies.  Get as much information as possible on each puppy, such as hips, elbows x-rays, eyes, thyroid, heart.
70% of all dog diseases are autosomo-recessive (Mom and dad are disease free, kids get the symptoms or disease)
Contribute to open data registry such as OFA – it enables tracking of health conditions vertically and horizontally within each line. 
6.) Data Analysis.  Learn how to and Fill out Genetic Pedigree for each litter, keep it updated.  Contribute to Open Registry
7). Conclusion.  What did you learn from this breeding.  How will you move forward with your breeding program?

 

Each breeding should be Planned.  How do you plan a breeding?  You need to decide what is important, set your goals, write them down, be objective.
Make a list in descending order of all the things that are important to you, for example:
*Temperament: CGC, Therapy dog
* Health: hips, elbows, heart, thyroid, etc.  You must evaluate ALL dogs in Pedigree
* Working Ability: Obedience, protection, drafting, agility, etc.
* Conformation

Principle of Genetics – to selectively breed for any of your objectives you need to know the basics of Genetics.  

Education.  As a breeder you have responsibility to your breed, to every puppy buyer, to every dog you produce.  Spend as much time planning what goes into your breeding genetically as much as you train and show your dogs.

DOG GENETICS. (review)

Dogs have 38 pairs of chromosomes. Plus sex chromosomes. One of each chromosomes in the pair comes form Mom, one from Dad.
Genotype – think Genetic make up (constitution) of a dog (think Alleles)
Phenotype – the way a dog looks or physical appearance/observable characteristics of a dog (think P- Picture for Phenotype).

Morphology – Conformation – structure, movement.

Dominant Alleles- Symbol- capital letter (ie. B for black coat) Parents and offsprings show traits of a disease, no carriers.
Recessive gene is expressed only when it is present in two copies or if the other copy is missing.
Recessive Symbol small (ie.letter aa).  Two identical copies needed

 

             Black Dogs for example BB or Bb look the same Phynotipically - they are black.  Dogs  bb are liver colour.

-       +

B

B

B

BB

BB

b

Bb

Bb

-       +

B

B

b

Bb

Bb

b

Bb

Bb

                                     

 Pure Black                  
Carrying liver     All carry liver colour colour


-       +

B

b

B

BB

Bb

b

Bb

bb

 

Phenotype: 75% Black, 25% liver
Genotype:  25% BB
50% Bb
25% bb
Dominant--A gene is said to be dominant if it expresses its phenotype even in the
presence of a recessive gene. (Example Bb in a black dog) Dominant Inheritance This means that the dog will be affected with only one copy of the disease gene.

 

Why purebred dogs have hereditary diseases?
1.  All dogs have limited the availability of genetic material, because genetically speaking, they are a  closed population.

  • Dogs of a specific breed have no new alleles available to the breed. 

Allele--Alternative forms of a genetic locus; a single allele for each locus is inherited separately from each parent, each locus may have multiple alleles possible however only two are available at a time, one from each parent.

  • The only gain in genetic diversity is through new mutations (usually undesirable traits and/or health issues)

Mutation--A permanent transmissible change in the genetic material, usually in a single gene. Also, an individual exhibiting such a change.

  • Over the years dog breeders came to a significant loss of genetic adversity.  Example- breeding specifically for one trait, which eventually leaves many  alleles virtually unavailable to the breed

 

  1. Founder Effect (what started the breed?)

Founder effect – Changes in allele frequencies that occur when a sub-population if formed from a larger one. Founders of the sub-population may have among them greater or lesser percentages of particular alleles than is the case for the population as a whole.

Portuguese water dogs are a good example of limited genetic material available to this breed.  6 original dogs account for 80% of current gene pool of this breed.  You can trace virtually any Portuguese Water Dog to one or more of the founding 6 dogs. 

3.  Popular sire effect or “matador”   One Champion who is successfully companied is excessively used in breeding, narrowing the already limited alleles in closed population to even fewer alleles.

70% of all inherited diseases are autosomal – recessive, which means there no or very few diseased animals in genetic pedigree, but many silent carriers.  Recessive Inheritance This means that a dog must have two disease genes in order to be affected with the disease.
Autosomes--A chromosome not involved in sex determination.

GENETIC PEDIGREE

  • Shows as many relative as possible vertically and horizontally (multiple generations and litters)
  • Track specific traits

 

Affected This indicates a dog which will -- or currently does -- show signs of the disease because it has two disease genes.
This symbol indicates a female.
This symbol indicates a male.
or These symbols indicate  clear dogs.

 

or These symbols indicate affected dogs.
These symbols indicate either diseased dogs.

 

Half coloured- carrier ( half good half bad)

 


Assemble a pedigree with as many litters as possible.  Broad is more important than deep in genetic pedigrees.  Make multiple copies and up date them as often as possible. Track still birth, early death, anything unusual.  It helps to evaluate diseased breeding stock, track disease, establish if it is sex-linked, dominant, recessive, etc.

Statistically speaking:
Sibling of an affected dog – 67% chance of being a carrier.
Sibling of a carrier- 50% chance of being a carrier
Offspring of affected- 100% chance of being a carrier
Parent of affected 100% chance of being a carrier
Affected 100%

 

X-linked Y chromosome is very small.  Hairy ears are Y-linked.

Genome – The complete nuclear DNA sequence of a species, including all variations.
Genotype --The genetic constitution of an organism. See phenotype.

Polygenetic – A trait resulting from the action of multiple genes.  The height and size.- additive effect.   In this case it doesn’t matter where the Alleles come from, they add up till it reaches the number where clinical manifestation occurs.
Hip and Elbow dysplasia is polygenetic, Nature vs Nurture- no such thing- they both play a role in cases with dysplasia.  Many structures come together: many bones, ligaments, muscles, tendons, cartilage etc. 
Rate of growth, weight of a dog, injuries, food, minerals, vitamins, level of physical activity, everything plays a role in dysplasia. For example 4 types of elbow dysplasia are inherited separately.

  • Osteochondritis dissecans (OCD)
    • OCD is a condition in which a piece of cartilage becomes partially or fully detached from the surface of the elbow joint. This results in inflammation of the lining of the joint and pain. 
  • Fragmented medial coronoid process
    • Fragmented medial coronoid process is a condition in which a small piece of bone on the inner side of the joint has broken off of the ulna bone. This piece of bone irritates the lining of the joint and grinds off the cartilage of the adjacent humerus (similar to having a pebble in your shoe).
  • Ununited anconeal process
    • Ununited anconeal process is a condition in which a fragment of bone on the back side of the joint has failed to unite with the ulna bone during growth. Normally this bony process fuses with the ulna bone by 20 weeks of age.  The breeds most commonly affected include German Shepherds, Bassets, Mastiffs, and St. Bernards
  • Elbow incongruency
    • Elbow incongruency is a condition in which the joint does not have perfect conformation, and the cartilage of the joint wears out rapidly. In simple terms the joint does not fit together well and the final result is progressive arthritis.

http://www.vetsurgerycentral.com/elbow_dysplasia.htm

Genetics of Behavior.  Silver foxes in Russia.  Polygenetic traits

Tame Silver Foxes are the results of nearly 50 years of experiments in  Russia to domesticate  the silver fox.     Two Russian tame foxes from the project. This group has only about one hundred specimens.

 Notably, the foxes did not only became more tame, but more dog-like as well: the new foxes lost their distinctive musky "fox smell", became more friendly with humans, put their ears down (like dogs), wagged their tails when happy and began to vocalize and bark like domesticated dogs.

The breeding project was set up by Russian scientist Dmitri Belyaev, encouraged by the Communist Party of the time because of its link with the aim to control and improve the human condition.

Now, Russian scientists have a number of tame foxes which are fundamentally different in temperament and behavior from their wild forebears. Some important changes in physiology and morphology are now visible, such as mottled or spotted colored fur, curly tails, floppy ears.  Ears, tails and colour change most likely linked to tameness.  Polygenetic inheritance of morphological and behavioral traits. http://www.answers.com/topic/tame-silver-fox
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