WEBSITE WAS UPDATED: 2/17/2024
PUNNETT SQUARES
Ever wonder how we predict what traits baby goats might have?
Let's talk about Punnett squares!
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If you've never seen one before, don't worry, they're not as complicated as they sound. Punnett squares are a simple chart that helps us predict what traits offspring might inherit from their parents.
Now, for those of you who've used Punnett squares before, you might find this familiar, but stick around for a quick refresher! For those new to the concept, let's dive in and make it simple.
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Here is a blank Punnett Square to start:
Imagine we have two parents whose phenotypes and genotypes we know:
Parent A
Phenotype: Gold
Genotype: A(wt)A(a)
Parent B
Phenotype: Blackbelly
Genotype: A(b)A(a)
Parent A's genotype will go on top, and Parent B's genotype will go on the side.
Parent A
A(a)
A(wt)
Parent B
A(a)
A(b)
Great! Now, there are four blank squares we need to fill in. Let's do it together!
STEP 1
A(wt)
A(a)
A(a)
A(b)
A(wt)
A(a)
=
A(a)
A(b)
A(wt)A(a)
STEP 2
A(wt)
A(a)
A(a)
A(b)
A(a)
A(wt)
A(a)
A(b)
A(wt)A(a)
=
A(a)A(a)
STEP 3
A(wt)
A(a)
A(a)
A(b)
A(wt)
A(a)
A(a)
A(b)
A(wt)A(a)
=
A(a)A(a)
A(wt)A(b)
STEP 4
A(wt)
A(a)
A(a)
A(b)
A(wt)
A(a)
A(a)
A(b)
A(wt)A(a)
=
A(a)A(a)
A(wt)A(b)
A(a)A(b)
That was easy! Now, lastly, rearrange the alleles in each square with the most dominant allele first and the least dominant allele second. In this Punnett Square, we only have to change the last square.
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Here is the final result:
Parent A
A(a)
A(wt)
Parent B
A(a)
A(b)
A(wt)A(a)
A(a)A(a)
A(wt)A(b)
A(b)A(a)
A(b) aka Blackbelly
is dominant to
A(a) aka No Pattern
so the order is switched
Each square represents a 25% chance.
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For Genotypes:
25% chance for A(wt)A(a) - appears Gold
25% chance for A(a)A(a) - appears Black
25% chance for A(wt)A(b) - appears Gold
25% chance for A(b)A(a) - appears Blackbelly
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Therefore, for Phenotypes:
50% chance for Gold
25% chance for Black
25% for Blackbelly
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Now, why is it that there is a 50% chance for Gold?
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25% chance for A(wt)A(a) = Gold allele A(wt) + No Pattern allele A(a) = a Gold goat.
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PLUS
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25% chance for A(wt)A(b) = Gold allele A(wt) + Blackbelly allele A(b) = a Gold goat.