Punnett Squares

I haven't posted on here yet this week. So here is a run down of what we have done so far!! We have moved from just simple dominant/recessive traits to showing how we can model mendel's laws with punnett squares and pedigrees.

There were no daily questions on Monday, we just continued our discussion about predicting genotypes based on phenotypes. Most of you seem to have a pretty solid understanding of WHAT a punnett square is and how to set one up. You had time though to work through that section in the book as well as move forward into more complex form of inheritance.

Tuesday: We started with a Daily Question

Achondroplasia is a genetic disorder of bone growth.

A=Allele for Achondroplasia

a = Allele for Normal Bone Growth

1st off: is Achondroplasia (Dwarfism) a dominant or recessive disorder? Well since i represented the allele with a Captial letter, we know it must be a DOMINANT disorder

Next: What is the GENOTYPE of someone who is HETEROZYGOUS for Achondroplaisa?

Aa and that person would have normal bone growth.

What is the PHENOTYPE of someone who is homozygous recessive?

They would nave NORMAL bone growth

Using a punnett square, find the chances that two people heterozygous for achondroplasia could have a normal child. There would be a 25% chance they would have a child WITH achondroplasia. See punnett square below

What does this MEAN then? That two dwarfs that are Heterozygous have a 25% chance of having an averaged sized child. Those of you who have followed Little People Big world can now see how this couple could have 2 children that were averaged size. What does that mean about THEIR genotypes?!?! They MUST be heterozygous. So EVERY time they have children, there is a 25% chance they will be average sized.