Elementary POW, December 2-6, 1996

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Background
Often when a person dies he leaves behind possessions or money to be split among his heirs. Sometimes it is unfair because the person who claims to be the child is really not, but walks away with a lot of money. A punnent square is a way to tell you what blood type you could possibly be by the blood types of your two parents - and it can tell you what blood types you can't be.
Problem
Mr. Stipe died and left all his money to his children. Claiming to be a third child, another young man sued for a share of the estate. Mr Stipe's blood type was already on record so the judge ordered blood tests for all the family members and the young man. After the blood tests, the judge dismissed the suit. Using the punnent sqaure, explain why.
Assumptions
Mr. Stipe's blood is dominant AB.
Mr. Stipe's wife's blood is dominant A.
Hints
A's blood types can be IA IA
B's blood types can be IB IB
AB's blood type can be IA IB
O's blood type can be i i
Use a punnent square to figure out the question. This is a punnent square. Lets say your mom's blood type is O and your dad's is dominant A. What are your possible blood types? i i x IA IA
       i       i       Phenotypes     Genotypes

IA   IA i    IA i      4 IA i         4 A blood types

IA   IA i    IA i
Your only possible blood types are 4 A blood types.

This week's mentors are from Mansel Nelson's chemistry class at Tuba City High School in Tuba City, Arizona.

Correct Solutions were submitted by:

Larry Forshaw, Conrad Kirby, Nathaniel Stein, Chris Schultz, Cara Semino, 
Josh, David, Jake, Katie, Ashley, Abby, Mark, Niki, Nichole, Dan, 
Dan, Bobby, Mike, Maria, Amy, Mrs Hayes' 4th grade Math class, 
Ben Clements, Brian Powers, Alexandra Heimos, Nathan Straus, 
Justin Weiss, Allison M., Jason, Philip, Thomas, Connie, Russel, 
Alex, Miss Seager, Kristal Tidwell.

Highlighted Solutions

Anne Bozak had a very good explanation for this problem:
The judge ordered to have the suit dismissed because the young man did not have the right blood type. The young man needed to either have a type A or a type AB blood type, but the young man had a type O or a type B blood type.
I found out the answer by drawing a punnent square. Before I drew it I needed to know what blood types Mr. and Mrs. Stipe had. Then I needed to know that a blood type can be called IA IA and AB blood type can be called IA IB.

Harrison Miller did not do this problem himself, but he has a wonderfully interesting story about it. This is what he had to say:
Hello once again! My name is Harrison Miller,and I go to Georgetown Day School in the 5th grade. I am 11 years old. My teacher's name is Paul Nass. He wanted me, when I told you my answer, to tell you this story.
My teacher thought that this pow was too hard. He did not require it or hand it out or even photocopy it. Well I knew that I was going to go to the allergist, who is actually a very close friend. I had forgotten to bring the problem home from school but I remembered about some kind of chart and about blood types. So for a couple of minutes, writing on the paper on the examining table, he told me about and reminded me of punnent squares. I took this paper and was happy and thought I had just the right idea of how to solve it and I was thiniking how easy it was. Then, when I tried it out, I found out I was basically where I started. I thought I was not going to get it when my brother (17) kicked in. He learned about punnent squares he said freshman year. Well anyway he said he got the answer that the man, (I believe the claiming 3rd child) must have had blood type O. I believe he used a punnent square for this.

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