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post #1 of 35 (permalink) Old 06-14-2007, 06:13 PM Thread Starter
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line breeding/in breeding

Okay this entire havanese breed issue has me really interested in genetics. My friend helped explain things to me the other night and then I did some searches. This one is on rabbits so I am not sure if the coefficients are different with dogs but I thought it gave you a good idea on in breeding and the good and the bad.

I have found lots of examples of why it is bad to in breed. Are there any examples of when it is good other than to produce a type? Have there been animals that have cured of an ailment from limiting the population quite a bit?

Amanda (who has a lot more reading to do!)

http://thhoppers.homestead.com/files...ccessfully.htm

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post #2 of 35 (permalink) Old 06-14-2007, 07:02 PM
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I am fascinated and confused with this as well. There are bound to be cons to inbreeding. I have much more reading to do as well, but on a quick google search I came up with this unusual one:

Inbreeding has been blamed for countless problems in dogs and cats, from hip dysplasia to reduced fertility. Researchers at the University of Pennsylvania believe that obsessive-compulsive disorder might be the next affliction to add to the list. Among its findings, their recent study investigating obsessive-compulsive disorder (OCD) in dogs and cats concluded that selective breeding and inbreeding may play a large role in the disorderís occurrence among companion animals.

The study, published in the Journal of the American Veterinary Medical Association (Vol. 221, No. 10),


I'm sure some breeders are very educated on the subject, as with most theories there are usually atleast two schools of thought.

Fire away oh knowledgeable ones!

Kara
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post #3 of 35 (permalink) Old 06-14-2007, 07:28 PM Thread Starter
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Kara,
I agree I can see how people can have completely different opinions but I think passionate breeders having discussions is completely great! I wonder just how much of the havanese health problems such as CD were started because of the lack of dogs in the U.S.?

And a photo just to show how bored my little girl is with all this reading of mine!

Time for a walk!
Amanda

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post #4 of 35 (permalink) Old 06-14-2007, 10:46 PM
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That photo is precious! Her look says it all. Mom- get off that darn machine and come play!

Wanda
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post #5 of 35 (permalink) Old 06-14-2007, 10:51 PM
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Amanda, I love that picture! It looks like she could be a blanket hanging there.

To answer your question about inbreeding getting rid of a disease, that's not really how genetics works. Let's say you have a mouse that has some kind of genetic mutation (recessive) that gives it some kind of disease. Now, when that mouse is inbred to another mouse from its litter it is possible that the second animal contains the same mutation. If that's the case, their offspring would contain 50% normal mice, 25% heterozygous (that has ONE of the recessive mutation) and 25% homozygous (diseased) mice. So, if there is some kind of recessive (or dominant) mutation that creates disease inbreeding can only make it worse, not better.

It is only recommended to inbreed if both mice (or dogs, or people or whatever) have perfect genomes (no mutations whatsoever). Otherwise, it's a game of chance, as it is with any breeding at all.

Lab mice, for example, are kept with specific phenotypes (whether it is wild type (normal) or some kind of heterozygous mutant) by inbreeding for many many many generations with no other side effects. In this case, as in all others, everything else is perfectly controlled. We know so little about environment creating disease that it is very important to keep all of the mice in the same exact environment eating the same exact food. This is VERY hard to do outside of a lab environment so it's hard to do the same with dogs (as pets).

Sorry for the long post... I tend to talk too much when it regards science since it's what I do for a living.
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post #6 of 35 (permalink) Old 06-14-2007, 11:01 PM Thread Starter
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Lina,
I didn't think of myself a science person (actually my major was philosophy!) but this is all very interesting! One of my good friends actually was telling me a lot about this type of thing and I have read a lot today so thanks for the clearification. I read about a lot of bad situations with people inbreeding and the outcome but I didn't know if there was evidence of how it could be good in the long run other than just producing a similar phenotype?

Amanda who made sure Dora got a good walk in!

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post #7 of 35 (permalink) Old 06-15-2007, 08:28 AM
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LOL Amanda!

My dog is so funny when she wants me off the computer. She'll jump up on the couch and literally use her paws to sweep my hands off my laptop and jump in my lap and demand attention!!! IT cracks me up everytime I mean, how can I resist?

She also gets mad at me if I sew too long w/o giving her attention, she'll whine at me until I get off my sewing machine to play with her.

Too cute.

Lina, thanks for the explanation. I also wonder how evolution of species factors into breeding back to a standard from the 1970's. Don't all species evolve to a small degree over a period of 40 years? Humans are MUCH bigger and taller than they were in the 70's.

Sorry if that wins the "dumb question" award, I'm an Economist, not a scientist. But couldn't just natural evolution account for some changes in size, coloring, or even changes in the animal's coat to adapt to its enviromment, etc.

Kara

Last edited by Thumper; 06-15-2007 at 08:31 AM.
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post #8 of 35 (permalink) Old 06-15-2007, 09:55 AM
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All the talk of line breeding and inbreeding has been interesting. Lo and behold, I logged in to read my online news sources and today this article appeared..
http://abcnews.go.com/Health/wireStory?id=3277785

Granted, it refers to people but the recent discussion of inherited diseases it seemed interesting. My apologies for it being off topic by referring to humans rather than dogs.

Susan

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post #9 of 35 (permalink) Old 06-15-2007, 10:07 AM Thread Starter
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Kara-I think that question makes a lot of sense. Although 40 years doesn't seem like much time but it is for humans (look at the weight changes too!) and then take the climate differences too.

Susan- I read that and it is very interesting with that community. Last night, I read about Ashkenazi Jews too. It made me think maybe what Dorthy did was the right thing outbreeding to a different line even if they were of different quality. What if she only breed the original dogs she had, maybe our havanese health problems would be out of control compared to what we have now. Just a thought!

Amanda

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post #10 of 35 (permalink) Old 06-15-2007, 10:28 AM
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Kara, yes you are right... small mutations can occur over time but your assumption that we are taller due to a genetic difference is not right. Think about it for a sec... a random mutation only occurs approximately every 1,000 bases. Now think of all the people who live in the US (for sake of argument), what would be the likelihood that they would all have the exact same random mutation to affect their size (height or whatever) at the same time? Really really really small.

The reason that is believed that people are taller/bigger nowadays is due to a MUCH better diet (especially during pregnancy - prenatal vitamins, no smoking or drinking, less caffeine and the such - basically everything your doctor told you not to eat/drink while you were pregnant that have been shown to affect the size of your baby) and better food. To a smaller extent, there are people who believe that all of the hormones that are placed into food to make them bigger can and do affects you and your body. I am not advocating organic food, or anything like that as I eat non-organic food myself, but that has been shown to be a more likely reason for people being taller now than a mutation in the entire population (as I said, very unlikely).

And yes, it's true... small genetic mutations COULD change color, size and differences to make the animal adapt but over 40 years?! The differences would be very small. I stress that I am talking about EVOLUTION, as you asked about... breeding (by humans) for a specific quality CAN produce the physical changes that you want over a much shorter time period.

In terms of evolution alone, except for the one or two odd dogs out (who got the correct mutation to affect their size, color, etc.) the large majority of the dogs will only have recessive mutations that will not change any aspect of their physical appearance. In order to do that, many many many generations have to pass with a heck of a lot of random mutations hitting the right gene. Animals adapt to conditions over HUNDREDS of years, not in decades.

Humans use the one or two mutations that pop up over generations, through inbreeding, to produce a dog that looks a certain way or has an interesting characteristic, or whatever. Breeding of dogs towards a specific characteristic is in short a way to cheat the many years of evolution and even to cheat it all together (producing a dog that is not necessarily healthy or viable for their environment and in the wild would die out - basic natural selection).

Last edited by Lina; 06-15-2007 at 10:31 AM.
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