Reptile & Amphibian Forums

Well, now we have a Glossary. Thanks to Paul Hollander and Jeff Nichols (shadindigo) for their help in putting it together. It took a little while but now it's there. Here's the link:

Glossary

There you'll find explanations and definitions of hopefully most of the words and terms unique to herpetology, herpetoculture, husbandry and biology of reptiles (at least those that you're likely to encounter in these forums) as well as explanations of sexing codes (ever wonder what 1.1 EDB means?) and a very basic overview of taxonomy and classification.

Suggestions are welcome. I am by no means perfect and certainly don't know everything...if I got something wrong or left something out that you think is important, please email me and let me know.

Enjoy!

This is really awesome! Thanks!!!

Judy
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1.0 red cape gopher (Caesar)

n/p

Great work, oldherper!

I read some of them, will have to scan the rest later.

Just a pointer, your definition of codominance is a little off.

A codominant trait is one where the heterozygote phenotype is intermediate between the two homozygous phenotypes.

In the hobby we generally don't differentiate between incomplete dominance and codominance.
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Chris Harrison

...he was beginning to realize he was the creature of a god that appreciated the discomfort of his worshippers - W. Somerset Maugham

OK...Thanks Chris. I'll take a look at that one. If you find others that you would suggest change for, please email me with them and I'll look at changing them. I appreciate the input. I would prefer to work via e-mail to correct any problems in the Glossary in order to avoid starting debates in the forums....one person says it should be "x", another says "y", then you get one arguing for "z" and tie up the forums for something that we could figure out offline, you know?

If you don't mind, Chris...please scan over the Glossary when you get a chance and E-mail me with any other suggestions. Thanks!

Looking at that definition further, I have noticed a couple of things...we'll go ahead and discuss this one a little further in here, since we started it here. This one was Paul H's..I think he was trying to say the same thing you said, but worded it differently. I also think that we need to find a way to simplify it a little since the whole idea of the Glossary was to give people that have no Genetics or Biology background understandable definitions to some of these words. We don't really want to send them looking up all of the other words in the definition if we can avoid it. The idea we are trying to get across is this:

Incomplete dominance= a blending of a dominant trait from one parent with a recessive trait from the other parent. Example: Red flower x white flower = pink flower.

Codominance= a mixing of a dominant trait from one parent with a recessive trait from the other parent. Example: Red flower x white flower= red and white spotted flower.

What do you think about removing the definition for "codominant" and replacing it with the one for "codominance" above and adding the one for "incomplete dominance" as shown above since "incomplete dominance" was left out in the first pass of the Glossary?

>>Incomplete dominance= a blending of a dominant trait from one parent with a recessive trait from the other parent. Example: Red flower x white flower = pink flower.
>>
>>Codominance= a mixing of a dominant trait from one parent with a recessive trait from the other parent. Example: Red flower x white flower= red and white spotted flower.
>>
>>What do you think about removing the definition for "codominant" and replacing it with the one for "codominance" above and adding the one for "incomplete dominance" as shown above since "incomplete dominance" was left out in the first pass of the Glossary?

This may be a semantic arguement, but when two alleles (traits) are codominant, there is no dominant or recessive allele. There are simply to codominant alleles. The same is true for incomplete dominance.

The key difference is that with incomplete dominance you get a het that is intermediate between the two. With codominance, you get a het that is a mixture of the two.

I agree with the idea of using both definitions (maybe with a "see incomplete dominance" statement at the end of the codominance definition and vice versa).

It might also be easier to define "codominant trait" rather than "codominance"?
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Chris Harrison

...he was beginning to realize he was the creature of a god that appreciated the discomfort of his worshippers - W. Somerset Maugham

Well, one...say the Red, is the "normally dominant" allele and white would be the "normally recessive" allele under Mendelian Genetics. In the case of a true dominant and a true recessive, you expect to get some white offspring and some red offspring from a mating between the two. The fact that some traits don't really work as Mendel outlined is where the whole "incomplete dominance" and "codominance" thing comes in. Rather than having a "one way or the other" phenotype in the offspring, you end up with one of two different kinds of blending. So, you are correct in that there isn't really a "dominant" trait and "recessive" trait in those cases, both alleles are both and exert their influences in the Filial phenotype and genotype. However, explaining that in one short paragraph is a bit of a challenge....so I have to try to simplify it as much as I can and just get the idea across without getting too deep into the genetic principles behind it.

>>>Incomplete dominance= a blending of a dominant trait from one parent with a recessive trait from the other parent. Example: Red flower x white flower = pink flower.
>>>
>>Codominance= a mixing of a dominant trait from one parent with a recessive trait from the other parent. Example: Red flower x white flower= red and white spotted flower.

A, AB, and B blood types in humans is the standard example of codominance. Red, pink, and white flowers is the standard example of incomplete dominance.

>>>
>>>What do you think about removing the definition for "codominant" and replacing it with the one for "codominance" above and adding the one for "incomplete dominance" as shown above since "incomplete dominance" was left out in the first pass of the Glossary?

As oldherper said elsewhere, the definition of "codominant" was mine. Looking at it now, I see the definition could be improved, and I will work with oldherper to do so.

I left out "incomplete dominant" on purpose. The idea was to have three and only three terms -- dominant, codominant, and recessive.

The appearance of an animal that is heterozygous for a recessive mutant is normal. The appearance of an animal that is heterozygous for a dominant mutant is like the appearance of an animal that is homozygous for that dominant mutant. The appearance of an animal that has a heterozygous codominant mutant can be distinguished from that of an animal that is homozygous for the normal gene and that of an animal that is homozygous for the codominant mutant gene. I really do not want to get into the "mixing" vs "blending" terminology. I think it is really confusing because mixing enzymes on the cell's level produces blending on the whole animal level.

Possibly the best solution would be to add a list of synonyms at the end of the definition of "codominant". These would include incomplete dominant, partial dominant, semidominant, transdominant, and half a dozen others.

>This may be a semantic arguement, but when two alleles (traits) are codominant, there is no dominant or recessive allele. There are simply to codominant alleles. The same is true for incomplete dominance.

100% correct.

>The key difference is that with incomplete dominance you get a het that is intermediate between the two. With codominance, you get a het that is a mixture of the two.

In both, on the cellular level, you get a het that has a mixture of both genes' enzymes. This produces an intermediate form on the whole organism level. The key similarity in both is that the heterozygous form is distinguishable from both homozygous forms. That's what I want to emphasize.

>I agree with the idea of using both definitions (maybe with a "see incomplete dominance" statement at the end of the codominance definition and vice versa).

I don't like either definition above. The latest definitions I've seen involve functionality vs nonfuctionality of the enzymes produced. Without knowing whether or not a gene produces a functional or nonfunctional enzyme, there is little point in trying to distinguish between codominance and incomplete dominance.

>It might also be easier to define "codominant trait" rather than "codominance"?

The word "trait" has its own semantic difficulties. IMHO, "codominant mutant" or "codominant mutant gene" is the best choice, if a change is made.

Paul Hollander