Some of you might know, I have a BS in Biology. Most of my genetic training has been in Mendelian Genetics and how genes are passed on from one generation to the next. This is great stuff to know when breeding dogs because it helps you determine coat color and understand how disease might be passed on and stay hidden from generation to generation. Here is a short video made for kids which explains the extreme basics of this concept and how it applies to dog breeding.
If you enjoyed that, here is a little game you can play to ‘breed your own puppies’. It shows exactly how hard it is to create a specific look.
Population Genetics is a separate field of genetic research. It involves looking at a population as a whole and how breeding practices will affect that population. This is extremely important when dealing with endangered species.
Why is Population Genetics important for a dog breeder? Well, if you look at breeds of dog who are ‘pure bred’ you must understand that the gene pool is limited to only dogs who are registered in such a way that their pedigree can be tracked back to a set of ‘founders’ who were also considered pure bred. This means the population you are dealing with is a closed gene pool, no new genes will ever come into the breed as long as the stud book is closed. With each generation you will lose genetic information if ANY puppy from a litter is spayed or neutered. These days almost everyone spays or neutered their pets, leaving only one or two puppies from a litter to carry genes forward to the next generation. What does this mean? Genetic diversity is extremely reduced (up to 90% if only one puppy is kept for breeding) with each generation. That is a sobering concept.
To better understand this I am taking two courses. One is on ‘general population genetic’ and the other will be focused on the problems we have in Poodles. I hope to post some of my insight here, in extremely summarized form so you can better understand my own breeding choices and what I hope to achieve with my program long term.
Here is what the instructor posted as her Summery of the course on basic population genetics:
Carol Beuchat PHD
I was asked for the “elevator pitch” I would give for my genetics class. Fair enough. Here it is:
1) All the useful genetic variation your breed will ever have was in the dogs that founded the breed. This genetic diversity is finite.
2) Every generation, alleles are lost by chance (genetic drift) and also by artificial selection by breeders, who select for dogs with the traits they like, and remove other dogs from the breeding population.
3) Because the stud book is closed, genes that are lost cannot be replaced.
4) So, from the moment a breed is founded and the stud book is closed, loss of genetic diversity over time is inevitable and relentless.
5) You cannot remove a single gene from a population. You must remove an entire dog, and all the genes it has.
6) You cannot select for or against a single gene, because genes tend to move in groups with other genes. If you select for (or against) one, you select for (or against) them all.
7) Breeding for homozygosity of some traits breeds for homozygosity of all traits. Homozygosity is the kiss of death to the immune system. And as genetic variability decreases, so does the ability of the breeder to improve a breed through selection, because selection it requires variability.
The consequences of inbreeding (in all animals) are insidious but obvious if you look – decreased fertility, difficulty whelping, smaller litters, higher puppy mortality, puppies that don’t thrive, shorter lifespan, etc. Genetically healthy dogs should get pregnant if mated. They should have large litters of robust puppies, with low pup mortality. Animals that cannot produce viable offspring are removed by natural selection.
9) Mutations of dominant genes are removed from the population if they reduce fitness. Mutations of recessive alleles have no effect unless they are homozygous. So rare alleles are not removed, and every animal has them.
10) Create a bunch of puppies that have a (previously) rare mutation, and the frequency of that bad allele in the population increases, so the chance of homozygosity increases.
11) Genetic disorders caused by recessive alleles don’t “suddenly appear” in a breed. The defective gene was probably there all along. Make a zillion copies, and you have a disease.
12) Using DNA testing to remove disease genes will not make dogs healthier (see 2, 5, and 6).
13) The breed will continue to lose genes (by chance or selection) until the gene pool of the breed no longer has the genes necessary to build a healthy dog.
14) At this point, the breed might look beautiful (because of selection for type), but will suffer from the ill effects of genetic impoverishment.
15) The only way to improve the health of a breed is to manage the health of the breed’s gene pool.
16) The health of individual dogs cannot be improved without improving the genetic health of the population. Population genetics provides the tools for genetic management of populations of animals.
17) Breeders can improve the health of the dogs they breed if they understand and use the tools of population genetics.
This is what my course is about.
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The general course has started and the first week of required reading has been a review of things I already know and understand. This is good, because it has been 20 years since I was in college. Population Genetics was touched on when I was in College, but in no way a focused course for me.
Here is the information on the Poodle specific class that will start after the general class is completed. http://www.instituteofcaninebiology.org/poodles.html No doubt about it, Standard Poodles are in sad shape. Auto Immune issues (Thyroid, Addisons, IBD, SA, IMHA, just to name a few) are the worst issues our breed faces and those issues are surfacing DUE to our breed’s loss of diversity in their genes. Hopefully this course will allow me to make better choices for the future of my beloved breed.
~Becky