Genetics questions you were afraid to ask... - Page 4

Hardwicki · #31 (**permalink**) 06-05-2008, 02:15 PM

Quote:

Originally Posted by Ssthisto

Ok.

In Royal Pythons, albino is a recessive. This means that one copy of the Albino gene (plus one copy of "not albino") looks exactly the same as no copies of the Albino gene. It takes having two copies of Albino to look visually albino. If you bred your normal male to an Albino female you would get all normal-looking offspring who are het for the albino gene. If you bred your normal male to a het albino female, you'd get all normal-looking offspring who MIGHT carry the albino gene - but there's no way to tell visually.

Now, so far, Spider appears to be dominant. This means that one copy of the Spider gene (plus one copy of "not spider") looks exactly the same as TWO copies of the Spider gene. There's no way to tell visually whether you have a one-copy heterozygous spider or a two-copy homozygous spider - but if it doesn't LOOK like a spider it doesn't carry the gene at all - there is no "invisible het". If you bred your normal male to a Spider female you'd reasonably expect at least some Spiders in the first generation; if you ever got a normal offspring, you know that your Spider female is a "het" Spider - she only carries one copy of the gene, and also carries one copy of the normal not-spider gene.

Mojave is a co/incomplete dominant gene. This means there's three distinct "looks" - if it's got no copies of Mojave, it is normal; if it has one copy of Mojave (AKA het Mojave) it is a visual Mojave, and an animal who has two copies of Mojave is a Super Mojave - a visually white/pale snake with a sort of smudgy pattern on the head. If it doesn't look like a Mojave or a Super Mojave it doesn't carry the Mojave gene at all - there is no "invisible het". If you bred your normal male to a Mojave female, you'd reasonably expect some Mojaves in the first generation; if you bred your normal male to a Super Mojave female, you would get all Mojave offspring in the first generation.

Um right...this is way more complicated than i thought it would be....

Ssthisto · #32 (**permalink**) 06-05-2008, 02:23 PM

What about it is particularly complicated, Vicky? As long as you remember that there are four rules, you can work out genetics for anything - from pythons to poodles to peas.

Dominant genes look the same whether you have one copy ("het") or two; only a no-copy animal looks different.
Recessive genes only show themselves if you have two copies; one copy ("het")looks the same as no copies.
Codominant genes have three different visual appearances - no copies looks different to one copy ("het") looks different to two copies ("super").

And selectively bred traits are made up of combinations of the other three gene rules, but no single gene has been isolated that controls that appearance.

Once you understand the rules, all you need to know is which rule any visual trait refers to and you can work out predictions based on that rule.

You just lucked out picking three royal python genes that corresponded to each of the three major rules - "high gold" in royals is probably a selectively bred trait.

leejay · #33 (**permalink**) 08-05-2008, 04:35 PM

if you bred a spider ball python to a normal for arguments sake we got 10 eggs
5 visual spiders
5 normal looking pythons

are the normals normal or are they het for spider????

Young_Gun · #34 (**permalink**) 08-05-2008, 04:54 PM

Quote:

Originally Posted by leejay

if you bred a spider ball python to a normal for arguments sake we got 10 eggs
5 visual spiders
5 normal looking pythons

are the normals normal or are they het for spider????

The normals will be normals, no difference in genetics to a Normal x Normal clutch.

Ssthisto · #35 (**permalink**) 08-05-2008, 04:59 PM

Quote:

Originally Posted by leejay

if you bred a spider ball python to a normal for arguments sake we got 10 eggs
5 visual spiders
5 normal looking pythons

are the normals normal or are they het for spider????

Nope, the normals are non-carriers.

Your SPIDERS are in fact the het for spider (there is no possible way they can be homozygous because they didn't have two spider parents)... because Spider is a dominant gene.

leejay · #36 (**permalink**) 08-05-2008, 05:49 PM

Quote:

Originally Posted by Ssthisto

Nope, the normals are non-carriers.

Your SPIDERS are in fact the het for spider (there is no possible way they can be homozygous because they didn't have two spider parents)... because Spider is a dominant gene.

thanks a lot Ssthisto
explained so i understand it as well

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