Genetic Testing


I Am A Rebel

Genetic testing is the latest, greatest and most wonderful thing that ever happened to breeding animals.  Excuse me but horse hockey.  If anything it might be one of the worst things that ever happened to breeding.  Let me explain why.

Lets Go To Purebred Island

I am big on turning ideas into pictures so lets imagine ourselves on an island.  On this island there are lots of cats.  These cats are all the same basic type but we are going to throw a bunch of them off of the island.  Why?  Because when people decided to start designating certain cats as purebreds it was a hobby for wealthy people and only a small percentage of the cats of a certain type were registered as purebreds.  This limits the gene pool significantly.  

The remaining cats are not just going to be allowed to breed indiscriminately either.  We are going to be picky.  Only some of them are going to be considered to be worthy of reproducing.  This is not a bad thing.  Some cats are better examples of the breed than others but it does limit the gene pool.  Some animals die without reproducing.  Others reproduce far too much.  No, that is not an ethical comment.  I am talking about genes not morals.  Cats have very limited morals when it comes to mating I assure you.  The problem is that no matter how wonderful any given male is you don't really want him to reproduce to such an extent.  Why?  Well because pretty soon a huge portion of the next generation is made up of his offspring.  

Now we are going to do something even more radical we are going to take our beautiful cats and break their island into pieces so that they are geographically isolated from one another just as Siberians were when the small population in the US was brought from their home in Europe.  We are getting down to bare bones here folks.  Problems are going to start cropping up.

Hillbillies And Hapsburg Jaws

I am from the mountains of Appalachia.  We have a reputation for marrying our kinfolk.  Guess who else does that... European Royalty.  In both cases the results are the same.  Down the road a few generations birth defects and genetic illnesses start cropping up.  Its a bad thing.

Queen Victoria was a very prolific mother producing 9 children.  England was a powerful country so all the princes of Europe wanted to form alliances through marriage to the English crown.  As a result her bloodline was spread throughout the better part of the royal families of Europe.  Along with the political connections this also resulting in the spread of what was known as "The Royal Disease" which was actually a rare form of hemophilia.  

The branch of the Hapsburg family that ruled Spain is another prime example of inbreeding.  Have you ever heard of the Hapsburg Jaw?  Its not pretty.  The lower jaw juts out to an extent that can make chewing, speaking and even closing the mouth difficult or even impossible.  In Charles II who was the last Hapsburg to rule Spain this came to a culmination that was horrific for the poor man.  Not only did he have the issues that were caused by the jaw deformity he also was short, weak, impotent, mentally handicapped, suffered numerous intestinal problems, and did not even speak until he was four years old   That is quite a laundry list, isn't it?

The same thing happened up here in the mountains I love so much.  Tiny pockets of people who were kin to one another became isolated and inbred.  Sooner or later this took a horrible toll.  Children were born with devastating and painful deformities.  In our case people looked down on "stupid hillbillies" that didn't know better than to marry their own cousins but it was no different than the Hapsburg family or Queen Victoria.  In the end, it doesn't matter if you are a hillbilly, European Royalty of a cat you really need to avoid swimming in your own gene pool whenever possible.

Basic Genetics

Let's go back to our little island full of cats.  As we have been thinning out the genetic options bad things have been happening.  Kittens are not thriving.  Some are weak and sickly.  Others start out well and develop health problems later in life.  What do we do?  Well, for starters we don't let the imperfect kittens breed.  That means any kitten who has a dominate gene for a defect will not get a chance to pass it on but it does nothing about the ticking time bombs hidden in some of the cats genetic makeup.

Alleles are variations of genes.  Lets use eyes as an example.  Eyes have color.  Some are blue.  Others brown or green.  Which color you have is determined by mutations of the gene that decides the pigmentation of the eyes..   Each of us has two alleles for any given trait.  When our genetic make up is being decided at conception we get one of our alleles from each parent and the dominate one controls who will will be.

Lets go with my own family.  Mom had brown eyes but I know she carried a blue eye allele because I have blue eyes.  The same is true with Dad.  He had green eyes but had to carry a second allele for blue eyes or his green eye allele would have trumped Mom's blue eye allele..  I have a brother with brown eyes.  I do not know which allele he got from my father because Mom's dominate brown allele would trump either the blue or brown allele he contributed.  That means if they had more children brown eyes would have been twice as common as blue or green eyes.  Carrying this further if there were another child with Mom's blue eye allele like me but she got Dad;s green eye allele then she would have had green eyes because the green eye allele trumps the blue eye allele.  It sounds pretty complicated but in the end it just means that recessive genes can be hidden for generations never cropping up but laying in wait until two parents with the same recessive alleles meet and reproduce together.  Even then odds are against the recessive gene causing issues.

Now I like my blue eyes but lets suppose those blue eyes were a negative trait instead like a tendency towards cancer, heart disease or something else I would rather not have.  In some level it seems like it would be a good idea to avoid that combination cropping up, right?

Genetic Testing

This is where it starts to sound like genetic testing might be a good idea.  After all, if you just eliminate those "bad" genes the whole problem goes away.  Right?  Nope life isn't that easy.  You see we are more that just one genetic trait.  When you eliminate cats from that island we were talking about you are reducing the genetic options.  The longer you do it and the more cats you kick off the island the more the remaining cats are forced to breed with their family members.  Suddenly rare genetic traits that hardly ever showed up are becoming more and more common.  In a larger population these traits would not be an issue because the odds of two cats with the same trait meeting and mating would be very small but in this shrinking population the odds are distorted and otherwise rare genetic problems suddenly become common.

That isn't all.  Sometimes  a supposedly negative gene can have a positive effect we do not understand right away.  A good example is the genetic mutation that causes Sickle Cell Anemia in people of African descent.  Logically this genetic anomaly should disappear on its own because it is both a recessive genetic trait and shortens the life span thus reducing the chance to pass on ones genetic makeup to offspring.  BUT.... and it is a big but.... the way this gene affects the body also makes it so that someone who carries it is far less likely to develop Malaria.  In areas where the temperature is warm and moist enough to breed the mosquitoes who carry Malaria this supposedly negative gene actually is an asset.  People who have it often live longer and pass on more of their genetic material than those who do not.  Taken away from that setting though people find it to be a devastating illness.

My own ancestry is in part Native American.  In the fairly recent past my ancestors did not have as much exposure to high carbohydrate foods.  As a result their bodies developed an ability to get every bit of use possible from the carbohydrates they did have.  It worked great in a hunter gather society but now days it causes us to get diabetes etc. because we are not adapted to all the sugar, corn syrup etc. in our modern diet.  As long as there is easy access to cheap carbohydrates it is a problem but the world is not static.  Things change.  Should food be harder to come by again then this thrifty gene would once again be an asset.

The same things that are true with humans are true with cats.  We are very linear creatures and often miss the secondary effects of our actions.  It is sadly part of human nature to play God before we fully understand the consequences.  Right now the companies that do the genetic testing are making a lot of money telling people about the short term benefits of genetic testing without looking at the long term damage it will do to the breeds we love so much.   

The Cure

If you want to prevent genetic illnesses the cure is not to reduce the gene pool but rather to expand it.  I brought half of my genetic stock (cats) from Europe.  Why?  Because they were carrying fresh genes.  They were still pure bred Siberians but not as closely related to the cats I bought here in the US as they would have been otherwise.  That is step one.  Just quit marrying your cousins folks and don't ask your cats to do it either.  Simple, huh?

OK, what else?  Go look at my page on diet and you will see that most disease that we are doing genetic testing for are either preventable or likely to show up late in life.  The truth is your cat is far more likely to die from the results of a bad diet or too little wet food than from a genetic illness.