Genetics 101 ~ Part 2

Quite a while back I started a series on genetics, you can find the first post here, so to pick up where I left off…a puppy receives 50% of it’s genes from the sire and 50% from the dam. There is no way to know what half they will get or to control that so responsible breeder’s try to breed dogs that are good specimens of their specific breed. This means dogs that are good representations according to their breed standard; you should study and know your breed standard. With my breed we do many health clearances before breeding, however with that being said you can do your very best at choosing a stud dog or dam and some of the pups in a litter will be better than others. You may also get some recessive genes pop up or threshold traits that account for certain diseases. When I did my breeding I did health clearances on Riva and I looked for that in the stud dog also, however clearances alone are not my deciding factor on breeding two dogs. I believe that the health clearances are to be used as a tool to help in the decision process and that looking at the WHOLE DOG, it’s ancestors and their offspring (progeny) in the first 2-3 generations is where the decision should be made on who I breed. I have read various articles on genetics and attended a wonderful seminar given by Claudia Orlandi on The ABC’s of Dog Breeding and also her seminar on Practical Canine Anatomy and Movement. This was a fantastic experience and I highly recommend both of these home study programs whether you are a breeder or not. Another good resource I have read on diversity, and this relates to Chesapeake’s, however the information transcends over to other breeds as well is located here

So on with the lesson…I thought I would talk about additive genes as they apply to polygenic traits (traits controlled by more than one pair of genes) today. An additive gene refers to such things as movement, forequarter and hindquarter angle, temperament, hunting ability, just to name a few. The better additive traits a dog has the more likely it carries good genes for that trait and the better chance it will pass these good genes on to the offspring. So in essence what you see on a dog is a good indication of what the dog will produce. This is a great help from a breeding stand point because you don’t have to guess what you are going to get because “what you see is what you get”! So if a dog has bad angles it is likely to pass that on to the offspring. For example one of the many things I looked at in a male was a good shoulder, I did not want to loose the good shoulder Riva has because that happens to be one of the traits that is hard to correct.

Additive traits also play a role in threshold traits which are linked to cryptorchidism, hip dysplasia, cardiomyopathy, luxating patellas, infertility, to name a few. It takes several genes to influence a threshold trait, the genes come from both the sire and dam but may not be in equal numbers from each. The threshold trait will not show itself in the dog unless a critical number of genes are inherited. It is a “all or none” additive effect, the dog either is or isn’t! For example if it takes 8 undesirable genes to produce cryptorchidism, a puppy who gets 5 from the sire and 3 from the dam will be cryptorchid but if the pup gets 4 from the sire and 3 from the dam they will not be cryptorchid because they have not reached that critical number, (threshold) of genes. Most threshold traits are associated with defects and are looked at as recessive traits. From a breeding stand point this is particularly challenging because the given puppy example carries a high number of the cryptorchid gene so if bred to a dog who also has cryptorchid genes the risk is higher of producing cryptorchid pups in the litter.

So I hope this was informative, it’s a lot to think about and just plain fascinating! I will try to get the next genetic post up much sooner.

Reference: Orlandi, C., ABC’s of Dog Breeding

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Genetics 101

Well the seminar was fantastic! Claudia Orlandi did a wonderful presentation, and hands on demonstration. I think Cheyenne was disappointed though, she had a different idea on how we should have spent our afternoon Winking smile 

Instead of just telling you about how good the seminar was I thought I would do a series on what I learned starting with the basics of genetics. I find the whole world of genes and how animals are put together absolutely fascinating, so here goes my first post of many, Genetics 101.

The father of genetics was Gregor Mendel through his work with plants and peas he discovered that traits don’t blend, you can find more information on him here.

Every dog has 78 chromosomes or 39 pairs in the cell of the nucleus, they are rod shaped structures. The 39th pair are the sex chromosomes and the other 38 pair are called autosomes; these determine things like the body structure and temperament. Along these chromosomes are the genes and they also come in pairs, one gene from each parent goes into making the puppy and the genes in each puppy of a litter are different.

Each pair of chromosomes are called homologous and the place a gene is located on the chromosome is called locus. There are dominant genes and recessive genes, when genes are the same either both dominant or both recessive they are called homozygous and are considered pure for a trait. Gene pairs that have one dominant and one recessive are called heterozygous, these are considered not pure. The dominant gene overrules the activity of the recessive gene.

Phenotype is the external appearance of the dog and genotype is the genetic make up of the dog. You can not tell by the phenotype what the genotype is because of the hidden recessive genes. So I will stop here  and show you a few pictures from our day…

 

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                     Cheyenne being examined

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Our friend Chemmy

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Maybe the ducks are over there…what no ducks

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Watching the dogs

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                  Hey where did everyone go

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Chemmy and her mom

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              Cheyenne loves her Uncle Dave

 

So that’s it for today, stay tuned for more Genetics 101 in the weeks to come.

Claudia Orlandi Seminar

This Saturday I am attending a seminar on breeding and anatomy; this is being presented by Claudia Orlandi, Ph.D.. She wrote the book “ABC’s of Dog Breeding” which is a home study program covering the genetics of breeding. I read and took the test in the back of the book a couple years ago, sent my test in to the AKC and received a completion certificate.DSCN0887 (2)

I have been waiting for a long time for her to come to Michigan again to give her seminar and now she is finally going to be here and not only will I get to hear her lecture on this book I will have the pleasure of hearing the lecture on the “Practical Canine Anatomy and Movement

But wait it gets better, they have had such a large group of people register that they did not have enough dogs to use for the hands on anatomy section so they sent out an email requesting dogs. I thought about it and figured what the heck I will volunteer Cheyenne and great news they accepted my offer. So not only do I get to attend a seminar I have been waiting a long time for my beautiful Cheyenne gets to go with me. My friends over at Dusty Rose Chesapeakes will also be attending with one of their dogs, in fact it is because of them that I know about this book.

I love to learn all I can about the genetics and structure of dogs and I think you can never stop educating yourself. There is always something new to learn and in the long run it helps to make you a better breeder.