Sunday, December 17

Punnent Squares For Recessive Traits

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When I do punnent squares I always use N to denote wild type or Normal, recessive traits are denoted by small case letters, therefore an albino would be represented by ‘aa’ and a heterozygous albino would be represented by ‘Na’.  The punnent square for the breeding of an albino to a heterozygous albino would be as follows.

a

a

N

Na

Na

a

aa

aa

As you can see in the punnent square‘Na’ represents the heterozygous albino and ‘aa’ represents the albino in a het albino to albino breeding.Therefore each egg has a 50% chance of being either an albino or a het albino.

N

a

N

NN

Na

a

Na

aa

In this punnent square we have a het albino to het albino breeding.Each egg in this example has a 25% chance of being normal, 50% chance of being het albino and a 25% chance of being albino.Because we can’t visually tell the difference between a het albino and a normal the normal appearing babies from a het to het breeding are called 66% possible het albino, as 2/3 of the normal appearing babies should be heterozygous for albino.

N

N

N

NN

NN

a

Na

Na

This punnent square depicts a het breeding to a normal animal.In this pairing you would end up with each egg having a 50/50 chance at being het albino.Again because we can’t tell the het albino from the normal animals we call all the offspring 50% possible het albino because they have a 50% chance of being het albino, only way to prove it though is to breed it to a het albino or to an albino.

a

a

N

Na

Na

N

Na

Na

In this punnent square for recessives is the visual albino to Normal animal, as you can see you would end up with all the offspring being Heterozygous albinos.This is because one parent carries only the mutant albino gene and therefore can not pass on the wild type or normal look, so each egg receives the mutant gene from the normal and has to receive the normal gene from the normal parent.

a

a

a

aa

aa

a

aa

aa

In this final punnent square for recessives is the visual albino to visual albino, as you can see you would end up with all the offspring being visual albinos.This is because both parents carry only the mutant albino gene and therefore can not pass on the wild type or normal look.

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