Leatherback Beardies are they a dominant or recessive trait?

In a response to silkies the writer wrote …So if you breed two dominant leatherbacks together you would get 25% normal scale, 50% leatherbacks & 25% silkies or scaless … If you do the Punnett square for a recessive trait this is what you would expect.

I would suggest that Leatherback is actually an Autosomal Recessive gene similar to Sickle Cell Anemia in humans. Where the recessive gene is expressed as a phenotype when heterozygous. But is expressed as a “Silkie” when it is homozygous.

Opinions?

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Check this out!
Our team has put this together.

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By definition, a recessive gene does not have a phenotype in the heterozygous form. Genes that behave that way are called “incomplete-dominant”

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Yes, it is referred to as “incomplete dominance”
This article is a well stated explanation of dominance .Genetic Dominance & Cellular Processes.
It is also possible that “Leatherback” is a result of polymorphisms, which could explain the variations seen.
Also it should that there are two ways of discussing a gene. One is how it is expressed i.e. what it does within the body chemistry. And Two its’ relationship to other genes. Thus Leatherback has incomplete dominance in the first instance and autosomal recessive in the second. To calculate a Punnett Square you would use the second.
The terms penetrance and expressivity quantify the modification of the influence on phenotype of a particular genotype by varying environment and genetic background; they measure respectively the percentage of cases in which a particular phenotype is observed when the specific allele of a gene of interest is present and the extent of that phenotype.

Many disorders are inherited in an autosomal recessive manner.

Genetics, Autosomal Recessive

Thus to sum up. The manner in which the Leatherback or Silkie gene is expressed is incomplete dominance. The manner in which inheritance is calculated is autosomal recessive.

While this seems nit picking, it helps clarify the inheritance (only if it is a single gene :slight_smile: )

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Within the hobby, there are many ways we discuss genes but yes, primarily we only focus on two of them. Unfortunately, the majority of the hobby, yourself included, are discussing them incorrectly. There is how a gene is expressed: recessive, incomplete-dominant, dominant, sex-linked, etc. and there is how the gene is inherited: dominant or recessive.

The relationship a given gene has with other genes is, among other things, polygenetic or epistatic. There is nothing about Leatherback that indicates it falls under either of these.

A Punnett square is used to calculate the statistical potential a given pairing can produce. That is all.

On the basis of nothing but the shorthand used to draw out a Punnett square, both recessive and incomplete-dominant share the same pattern however, that does not change the fact that you set up the square based on the behaviour of the gene. You do NOT use the appearance of the square to define the identity of the gene.

The “variety” of Leatherback appearance that you are discussing is nothing more than variation in animals that is the result of some of the ~20,000 other genes in the animal (the “expressivity” you note, which is wholly different from penetrance). We see this across all Mendelian traits. All blue eyes are not the exact same shade of blue. All Pastels are not exactly the same degree of “yellow”. All wrinkled peas are wrinkled in exactly the same way. But again, none of that has anything to do with the inheritance of the specific gene responsible for the mutation or the expression pattern of that gene.

Leatherback is inherited in a dominant manner (e.g., any animal with a single Leatherback gene has a non-wild-type phenotype) and it is expressed in an incomplete-dominant manner (e.g., an animal with one copy of the gene has a phenotype different than an animal with two copies of the gene.)

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Lets take this offline.
email me at animalspecialties@gmail.com
for a reply
Thanks
Paul

After reading your response several times. I realized that your
response was written quickly without looking back at what I had said.

I say this because I stated exactly the same things that you stated.
There is no difference between us and The statement at the beginning of
your reply

(yourself included, are discussing them incorrectly) is simply in error.

Examples of similarities:

My statement …
Also it should be there are two ways of discussing a gene. One is how it is expressed i.e. what it does within
the body chemistry.

And Two its relationship to other genes.

Thus Leatherback has incomplete dominance in the
first instance and autosomal recessive in the second.

Your statement:
There is how a gene is expressed: recessive, incomplete-dominant, dominant, sex-linked, etc.
and there is how the gene is inherited: dominant or recessive.

These two statements are EXACTLY the same.

My statement
To calculate a Punnett Square you would use the second. …( i,e, for a single recessive trait)

This is ALL I say about a Punnett Square.
Yours
Punnett square is used to calculate the statistical potential a given pairing can produce. That is all.

Nowhere do I say the following
Your statement
On the basis of nothing but the shorthand used to draw out a Punnett square, both recessive and
incomplete-dominant share the same pattern however, that does not change the fact that you set up
the square based on the behaviour of the gene. You do NOT use the appearance of the square to define
the identity of the gene.

The definition of a Punnett Square in wikipedia
The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment.

================================================

My statement

The manner in which the Leatherback or Silkie gene is expressed is incomplete dominance.

Yours
it is expressed in an incomplete-dominant manner

Exactly the same.

This statement has no relevance

your statement.
(the “expressivity” you note, which is wholly different from penetrance).

I defined these terms only. Did not equate them in any manner
my statement
The terms penetrance and expressivity quantify the modification of the influence on phenotype of a particular
genotype by varying environment and genetic background;
they measure respectively the percentage of cases in which a particular phenotype is observed when
the specific allele of a gene of interest is present and the extent of that phenotype.

================================
My closing statement
Thus to sum up. The manner in which the Leatherback or Silkie gene is expressed is incomplete dominance.
The manner in which inheritance is calculated is autosomal recessive.

Yours
Leatherback is inherited in a dominant manner (e.g., any animal with a single Leatherback gene has a
non-wild-type phenotype) and it is expressed in an incomplete-dominant manner (e.g., an animal with one
copy of the gene has a phenotype different than an animal with two copies of the gene.)

The same!!

==========================================
I also feel that the appropriate reference to the recessive gene would be “Silkie” as Leatherback is only the incomplete dominance
expression of the “Silkie” gene. While Leatherback is still a valid reference to its expression as a recessive trait.

I again refer to the manner in which human genetic disorders, like Sickle cell anemia, are referenced
i.e.

another well-known autosomal recessive Sickle cell disease

Sickle cell disease also exhibits incomplete dominance and haploinsufficiency.
Individuals who carry a single disease allele (heterozygotes) have an intermediate trait
(sickle cell trait) that is phenotypically somewhere between unaffected (homozygous normal allele)
and severely affected (homozygous disease allele giving rise to sickle cell anemia).
These individuals are not considered completely unaffected, hence incomplete dominance.

You attempt to use the Punnett square for a recessive trait as justification for your argument that Leatherback is recessive:

Below are six Punnett squares. Each represents a proven morph in the hobby.

Please identify which is/are recessive, which is/are incomplete-dominant, and which is/are dominant.






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Again you miss the point.

I do not reference a Punnett Square to determine whether it is recessive or incomplete dominant as these reference different views of the same thing.

Your statement:
There is how a gene is expressed: recessive, incomplete-dominant, dominant, sex-linked, etc.
and there is how the gene is inherited: dominant or recessive

What I have said over and over again. It would appear from literature is that the manner in which this particular trait is inherited may be best called recessive. While the way it is expressed is incomplete dominant.
This is in complete agreement with your statement above.

As I have stated below. I don’t know why you keep trying to disagree with this view, when in your statements you say the same things as I have stated, as below.

The Silkie gene is recessive. The Leatherback phenotype is the incomplete expression of this recessive gene.

I also feel that the appropriate reference to the recessive gene would be “Silkie” as Leatherback is only the incomplete dominance expression of the “Silkie” gene. While Leatherback is still a valid reference to its expression as a recessive trait.

==========================================
I again refer to the manner in which human genetic disorders, like Sickle cell anemia, are referenced
i.e.

another well-known autosomal recessive Sickle cell disease

Sickle cell disease also exhibits incomplete dominance and haploinsufficiency.
Individuals who carry a single disease allele (heterozygotes) have an intermediate trait
(sickle cell trait) that is phenotypically somewhere between unaffected (homozygous normal allele)
and severely affected (homozygous disease allele giving rise to sickle cell anemia).
These individuals are not considered completely unaffected, hence incomplete dominance.

Thus:…
Silkie also exhibits incomplete dominance and haploinsufficiency.
Individuals who carry a single allele (heterozygotes) have an intermediate trait
*(Leatherback trait) that is phenotypically somewhere between unaffected (homozygous normal allele)*and severely affected (homozygous allele giving rise to Silkie).
These individuals are not considered completely unaffected, hence incomplete dominance.

If these traits were to appear in the wild. Leatherback would survive and Silkies would die. Thus this could be considered the equivalent of a disease trait.

==================================================================

I’d like to point out that there are two lines of Leatherback in Bearded Dragons, one incomplete dominant and one that is recessive. The latter is referred to as “Recessive Leatherback.”

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You can “yell” all you like with your bold giant font but it does not change the fact that you are mistaken in your understanding

A recessive trait is one where you only see a phenotypic change in the animal when both copies of the gene are mutant. Silkie does not meet those criteria because when one copy of the mutant gene is present there is a very clear phenotype - Leatherback

When you have an actual recessive, like Albino for example, the genetically heterozygous animals are indistinguishable from the genetically homozygous wild-type. This is very obviously NOT the case with Leatherback/Silkie because there is the well documented and named Leatherback description for the heterozygote

Further, recessive traits are occluded by the opposite allele to them. So when you breed a visual recessive to another animal that does not carry the recessive gene, none of the offspring will show an altered phenotype. This is why when you breed an Albino to anything that does not carry the Albino gene, all of the babies have the wild-type phenotype. Again, this is very obviously NOT the case with Leatherback/Silkie because if you breed a Silkie to anything that does not carry the gene, all of the offspring will exhibit the well documented Leatherback phenotype for the heterozygote

Additionally, recessive follow a two phenotype expression with a 3:1 ratio where as incomplete dominant follow three phenotype expression with a 1:2:1 ratio whereas dominant follow two phenotype expression with a 1:3 ratio

Again, Leatherback/Silkie show the three phenotype 1:2:1 pattern

There is absolutely nothing about Leatherback/Silkie that falls under the category of “recessive"

It is a dominantly inherited gene that exhibits incomplete-dominant expression.
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.
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I was not aware of this and I appreciate you flagging it to my attention. That said, a quick look at some of the literature on the recessive one is that you only see the “LB” trait in the homozygous form and breeding two of these visuals “rLB” together will not produce a Silkie. So while that trait does exhibit an actual recessive inheritance pattern, it is a completely different mutation than the one the OP is talking about here as they have numerous times referenced the Silkie.

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Correct, the two types of Leatherback are completely separate mutations.

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This is why I love being on a forum with you @t_h_wyman.

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First I would like to apologize for what you took as Yelling. I did not intend for that post to come off as yelling. I composed it off line in a text processor and then copied it into the simple wysiwyg editor of the forum. Which promptly took what was underlining and bold for emphasis and changed to what you see. Again just emphasis not yelling.

however to the point. You, @t_h_wyman wrote…

"that said, a quick look at some of the literature on the recessive one is that you only see the “LB” trait in the homozygous form and breeding two of these visuals “rLB” together will not produce a Silkie.

I have searched and have not been able to find the “literature” you mention.
Could you post links to this literature. I would very much like to read it.

Thanks

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https://bdobsession.org/morphs

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