A lesson on probabilites with double recessives

I am very grateful for this post. I cannot figure out a punnet square to save my life, but even a dingaling like me can understand this. I am subscribing to this thread.

Gale

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Originally Posted by paulh

916 normal (66% probability het caramel, 66% probability het pied)
3/16 caramel (66% probability het pied)
3/16 pied (66% probability het caramel)
1/16 caramel pied
The fractions are the probability of an outcome per baby. They are not the probability per clutch.

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This is what I was wondering about. I understand that the fraction is per baby. The 66 percent is what I was looking for. How did you arrive at that? Isn't the percentage het for just pied or caramel different than the percentage that it is double het for both?



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Quote:

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Originally Posted by scooter11

This is what I was wondering about. I understand that the fraction is per baby. The 66 percent is what I was looking for. How did you arrive at that? Isn't the percentage het for just pied or caramel different than the percentage that it is double het for both?



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Each snake has a 66% chance of being het.

Say you have a het albino x het albino, genetically you get

Male:	Het Albino
Female:	Het Albino
Percent	Fraction	Traits
25%	1/4	Albino
50%	1/2	Het Albino
25%	1/4	Normal
View Results Page

but you cannot tell the difference between the normal and the het albinos. But you do know you are twice as likely for them to be het than not, which is a 2:1 ratio or 66%:33% (we round numbers down for some reason).

Male:	Het Albino
Female:	Het Albino
Percent	Fraction	Traits
25%	1/4	Albino
75%	3/4	66% Possible Het Albino
View Results Page

I also get a feeling this might need to be said, adding more genes into does not actually change your chance at getting the single gene, just that single gene may or may not have more genes in it. for example with albino again, adding the albino lines and het albino lines, you still have a 25% chances at an albino and a 75% chance at a het albino, just it may have other genes.

Male:	Het Albino, Het Piebald
Female:	Het Albino, Het Piebald
Percent	Fraction	Traits
6.25%	1/16	Albino, Piebald
18.75%	3/16	Albino, 66% Possible Het Piebald
18.75%	3/16	Piebald, 66% Possible Het Albino
56.25%	9/16	66% Possible Het Albino, 66% Possible Het Piebald
View Results Page

even with triples:

Male:	Het Albino, Het Clown, Het Piebald
Female:	Het Albino, Het Clown, Het Piebald
Percent	Fraction	Traits
1.5625%	1/64	Albino, Clown, Piebald
4.6875%	3/64	Albino, Piebald, 66% Possible Het Clown
4.6875%	3/64	Albino, Clown, 66% Possible Het Piebald
14.0625%	9/64	Albino, 66% Possible Het Piebald, 66% Possible Het Clown
4.6875%	3/64	Clown, Piebald, 66% Possible Het Albino
14.0625%	9/64	Piebald, 66% Possible Het Clown, 66% Possible Het Albino
14.0625%	9/64	Clown, 66% Possible Het Piebald, 66% Possible Het Albino
42.1875%	27/64	66% Possible Het Piebald, 66% Possible Het Clown, 66% Possible Het Albino
View Results Page

I ordered that book today so I'll let you know after I'm done reading it in six years. Since that's how long it is going to take me to understand its contents. Haha

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Quote:

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Originally Posted by scooter11

This is what I was wondering about. I understand that the fraction is per baby. The 66 percent is what I was looking for. How did you arrive at that? Isn't the percentage het for just pied or caramel different than the percentage that it is double het for both?

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I haven't been on for a while. Sorry.

916 normal (66% probability het caramel, 66% probability het pied)
3/16 caramel (66% probability het pied)
3/16 pied (66% probability het caramel)
1/16 caramel pied

The normals have a 66% probability for being het pied. They also have a 66% probability of being het caramel. This is not the same as a 66% probability of being both het pied and het caramel.

A normal has a 66% (2/3) chance of being het pied and a 33% (1/3) of being normal.
A normal has a 66% (2/3) chance of being het caramel and a 33% (1/3) of being normal.

A normal is either het pied or normal and either het caramel or normal. Make a branching system. Multiply the fraction in each branch.

_____________2/3 het caramel = 4/9 het pied and het caramel
2/3 het pied <
_____________1/3 normal = 2/9 het pied

_____________2/3 het caramel = 2/9 het caramel
1/3 normal <
_____________1/3 normal = 1/9 normal

So the percentage a normal looking offspring is het for both is what 44%? Or is that wrong

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me: :rolleye2:

Quote:

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Originally Posted by scooter11

So the percentage a normal looking offspring is het for both is what 44%? Or is that wrong

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44% is correct.