Genetics ?? Hypo gene specifically - Page 3 - FaunaClassifieds
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Go Back   FaunaClassifieds > Reptile & Amphibian - General Discussion Forums > Genetics, Taxonomy, Hybridization

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Genetics, Taxonomy, Hybridization General discussions about the science of genetics as well as the ever changing face of taxonomy. Issues concerning hybridization are welcome here as well.

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Old 10-17-2005, 07:19 AM   #21
crotalusadamanteus
Well, I admit that I have not used words like "phenotype, genotype, alelle, and loci" since high school. Boa genetics were explained to me in simple "english". Never in a manner such as this. But I don't mind, it's actually pretty interesting. And a good explanation of how the gene works.
I know that homozygous is "Having the same alleles at a particular gene locus on homologous chromosomes." Usually expressed correct?
I know that heterozygous is "Having different alleles at one or more corresponding chromosomal loci." Not expressed usually, correct?
And I do pretty much understand what you are saying. And believe it or not, it does make some amount of sense to me. It just has to sink in. LOL
I think I'm stuck more on the "proof" stuff. It's easier to believe what you see. And I have not seen a normal, from a litter of salmon, produce anything but normals. Than again, I have not had years of morph breeding experience. I rely on the info I have obtained from people that HAVE done it for a while. Perhaps I got lost on the explanations given.

I also will read the suggested " Mendel" and his pea plants. (No body knows so much, that they can't learn more, right?). Maybe it will help me to "better understand" as you put it.

M.Dwight.........Just curious why the "12" yr old off to the left? Sorta misleading don't you think? I had my doubts as to the age once i read your first post. Not spoken like most 12 yr olds. LOL
 
Old 10-17-2005, 09:47 AM   #22
Serpwidgets
Quote:
Originally Posted by crotalusadamanteus
I think I'm stuck more on the "proof" stuff. It's easier to believe what you see. And I have not seen a normal, from a litter of salmon, produce anything but normals. Than again, I have not had years of morph breeding experience. I rely on the info I have obtained from people that HAVE done it for a while. Perhaps I got lost on the explanations given.
This is because a normal is not carrying any copies of the Salmon mutant. If it were, the snake would not be a normal. The only way a normal "sibling to salmon" would have salmon offspring is if its mate were carrying the mutant gene.

When you cross a salmon to a normal and get normals and salmons, it all makes sense when you look at what is happening underneath the hood... the normal is S<sup>+</sup>S<sup>+</sup> (homozygous normal) and the salmon is S<sup>+</sup>S<sup>S</sup> (heterozygous normal and salmon) and the Punnett square for this cross reflects the results you expect:

<table border=1><tr align=right><td> </td><td>S<sup>+</sup></td></tr>
<tr><td>S<sup>+</sup></td><td>S<sup>+</sup>S<sup>+</sup></td></tr><tr><td>S<sup>S</sup></td><td>S<sup>S</sup>S<sup>+</sup></td></tr></table>

The normal (on top) is giving the wild-type allele to all offspring, the salmon (on the left) is heterozygous and thus giving the wild-type to some, the salmon mutant to others. The resulting genotypes in the litter are normal (homozygous or genotype S<sup>+</sup>S<sup>+</sup>) and the salmons are hets (S<sup>+</sup>S<sup>S</sup>)

Obviously a normal will not throw the salmon mutant to any of its offspring, because it does not have a salmon mutant to give. Nobody is saying that a normal is het for salmon. But a salmon is het for salmon and wild-type at the salmon locus, the same as a "normal het for albino" is a normal het for albino and wild-type at the albino locus. What is being called a "super salmon" is simply homozygous for the salmon mutant at the salmon locus.
 
Old 10-17-2005, 02:46 PM   #23
M.Dwight
Quote:
Originally Posted by crotalusadamanteus
M.Dwight.........Just curious why the "12" yr old off to the left? Sorta misleading don't you think? I had my doubts as to the age once i read your first post. Not spoken like most 12 yr olds. LOL
Sorry about that. That developed as part of an inside joke while in the chat room. And I forgot to change it back. I'll get to it however.
 
Old 10-17-2005, 03:09 PM   #24
M.Dwight
Charles, as always your post are right on the money. You should stop by here more often. The folks here seem to need your knowledge.
I have a fairly advanded grasp on genetics and cell biology right down to the nuclear level of DNA however my writting and teaching skills are lacking to say the least.
I'm glad we have you to explain it in a straight forward and logical manner.


Quote:
Originally Posted by Serpwidgets
Obviously a normal will not throw the salmon mutant to any of its offspring, because it does not have a salmon mutant to give. Nobody is saying that a normal is het for salmon. But a salmon is het for salmon and wild-type at the salmon locus, the same as a "normal het for albino" is a normal het for albino and wild-type at the albino locus. What is being called a "super salmon" is simply homozygous for the salmon mutant at the salmon locus.
It seems to me this is what trips so many people up. The understanding of what homozygous and heterozygous really mean. Once they understand that a het for albino is also a het for wild type and that a salmon boa is het for both wild type AND salmon the rest seems to fall into place.
 
Old 10-17-2005, 03:18 PM   #25
M.Dwight
And I need to remember to use the spell check
 
Old 10-17-2005, 06:16 PM   #26
crotalusadamanteus
OK,
I am starting to grasp what you are saying.............. I think. LOL
And actually it is very close to what I have been learning, just a different look, and explanation.

Where i got a lil lost was the difference between the co-dom, and dom genes. It was put to me, (in plain english) a Dom gene will affect the whole litter immediately. A co-dom gene will pass to a percentage of the litter, (any percentage). And a recessive gene will not affect the litter immediately, but the litter will pass the gene to their litters.

What I grasped from what was said above, this is not true. I do understand that a dom gene has two copies of the same gene, and a co-dom gene one copy of mutant, and one of WT. This goes with what I have learned. But I still sorta think its co-dom. Simply by the way it acts. A super salmon/WT produces all salmons theoretically. Because it has a Dom gene. A normal Salmon only produces some.

I'll go read that Pea thing. Thanks for everything so far. Been pretty interesting. So don't give up on me. LOL

Ciao,
Rick
 
Old 10-17-2005, 06:57 PM   #27
Serpwidgets
Quote:
Originally Posted by crotalusadamanteus
Where i got a lil lost was the difference between the co-dom, and dom genes. It was put to me, (in plain english) a Dom gene will affect the whole litter immediately. A co-dom gene will pass to a percentage of the litter, (any percentage). And a recessive gene will not affect the litter immediately, but the litter will pass the gene to their litters.
I think you are confusing "dominant" with "homozygous" and "codominant" with "heterozygous."

Dominant, codominant, and recessive are relationships between two alleles at the same locus. To put it in math terms, these are like Greater Than, Equal To, and Less Than.

Let's use two example alleles, call them A and a. Between any two alleles, there can be three genotypes: AA, Aa, and aa.

If one allele is dominant to the other, the other is recessive to it. In dominant/recessive relationships, there are two phenotypes. The AA and Aa genotypes create one phenotype, and aa creates a different phenotype.

If the alleles are codominant to each other, the three possible genotypes create three resulting phenotypes. That is, AA, Aa, and aa can all be visually identified.

----

Meanwhile, heterozygous and homozygous describe the same/different aspect of the pair of genes found at a locus. Homo means same, hetero means different. In math terms, these are kinda like Odd and Even.

If the gene pair is the same, it is homozygous.

If two different alleles are paired, it is heterozygous. It is also true that the individual is heterozygous for both alleles, since the pair cannot be "different" without two things to differ from each other. The wild-type is generally assumed when no second allele is mentioned. Thus, "het for albino and wild-type" gets shortened to "het albino."

So, AA and aa are both homozygous. They are not "dominant."

Aa is heterozygous. It is not "codominant."

I hope that made some more sense of it.

Using them as they are used in the above posts would be like saying that 7 is odd to 4 but even to 5, and even is less than odd.

In those terms, the results are explained a bit differently: The salmon allele is inherited by all offspring of a homozygous salmon parent, not because the gene is dominant, but because that parent is homozygous and thus cannot throw any other gene to its offspring. Since the salmon allele is dominant to the wild-type allele, and all of the offspring are carrying salmon, they will all express the salmon gene.
 
Old 10-17-2005, 11:43 PM   #28
M.Dwight
Lets go over the very basics.

A locus (loci for plural) is a space on a chromosome where genes live or exist.

Each locus contains two alleles.

Each locus will inherit one of these alleles from the father and one from the mother.

If a locus inherits two same or like alleles from the father and the mother then it is said to be homozygous.

If a locus inherits two unlike alleles (say one albino allele from the father and one wild type allele from the mother then it is said to be heterozygous.

The two alleles at a locus create a relationship with each other.

This relationship will determine which alleles will be visible in the phenotype.

A locus with two like alleles (homozygous) is always visible in the phenotype. An albino boa is visibly albino because it has inherited the two like alleles on the albino locus. Homo means same so both alleles are same or like.

If a locus has two different or unlike alleles it is heterozygous. And which ever allele is dominant will be visible in the phenotype.

In boas the wild type allele is dominant to the albino allele. So if a locus has one albino allele and one wild type allele then wild type will be visible in the phenotype. This locus has one alblno allele and one wild type allele so it is said to heterozygous for both alleles. But only one allele is dominant.

If a boa has one salmon allele and one wild type allele then salmon will be visible in the phenotype because salmon is dominant to wild type.

Dominant just means that it will be visible in the phenotype when paired with an unlike allele. The unlike allele on the same locus that is not visible in the phenotype is said to be recessive.
 
Old 10-18-2005, 12:59 AM   #29
M.Dwight
In my last post I basically explained the dominant/recessive relationship of alleles at a locus.

However, sometimes a locus will inherit two different or unlike (heterozygous) alleles and neither is recessive in relation to the other.

If neither is recessive then both must be dominant.

Remember dominant just means visable in the phenotype

Since both alleles are dominant and are working TOGETHER at the same locus we call this a CODOMINANT gene.

With a codominant gene Both allele will be visible in the phenotype.

If a locus has a allele for red and a allele for blue and red and blue are codominant in relation to each other then both red and blue will be visible in the phenotype.

Dominant, recessive and codominant are just words to explain the relationships of alleles at a given locus.
 
Old 10-18-2005, 02:20 AM   #30
M.Dwight
Quote:
Originally Posted by M.Dwight

With a codominant gene Both allele will be visible in the phenotype.
It would be more accurate to say..........
With a codominant gene both of the heterozygous alleles will express their traits in the phenotype.
But I was trying to keep it as simple as I could.
 

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