To Solve a Mystery Involving Genetics

Name

WHO

GET’S

THE

MONEY?

Purpose:

To solve a mystery involving genetics.

Background:

Mr. and Mrs. John Jones died in a tragic farm accident when the tractor they were riding on rolled over in a ditch. Authorities found three million dollars hidden in a feed bin in the chicken coop. The couple is known to have a son, from whom they are estranged. This man is the sole heir to the Jones fortune.

Five men show up, each claiming to be the couples’ long lost son who had run away to become a sheep-herder. You are called in as a genetics expert to decide who is the rightful heir. This mystery will be solved in three parts.

PART ONE: Complete Dominance (Dihybrid)

Brown eyes are dominant over blue eyes, free earlobes are dominant over attached earlobes.

Mr. Jones / Heterozygous free earlobes and dominant brown eyed
Mrs. Jones / Hybrid for earlobes and heterozygous for eye color.
Carl / Attached earlobes and homozygous brown eyed
Ray / Homozygous free earlobes, blue-eyed
Dale / Hybrid for earlobes, homozygous brown-eyed
Earl / Heterozygous free earlobes and heterozygous brown-eyed
Robert / Homozygous dominant for earlobes and blue-eyed

What are the genotypes of Mr. and Mrs. Jones?

What are the possible genotypes of the offspring?

Write each person’s genotypes in the chart below:

Person / Genotype
Carl
Ray
Dale
Earl
Robert

Which men can be eliminated by these traits? Explain your reasoning for each man.

PART TWO: Codominance and Incomplete Dominance

Now that ______have been eliminated, lawyers order blood tests to try to prove their claims. The lawyers have also done some research and read that hair texture is inherited.

Type A and Type B blood are codominant over Type O

Rh+ blood is dominant over Rh- blood.

Hair texture exhibits incomplete dominance. Homozygous (HH) have curly hair. Homozygous (AA) have straight hair. Heterozygotes (HA) have wavy hair.

Mr. Jones / Homozygous type A blood, heterozygous Rh+, straight hair
Mrs. Jones / Heterozygous type B blood, homozygous Rh+, wavy hair
Carl / Heterozygous type A blood, heterozygous Rh+, wavy hair
Ray / Type AB blood, homozygous Rh+, wavy hair
Dale / Heterozygous type A blood, homozygous Rh+, wavy hair
Earl / Type O blood, Rh-, straight hair
Robert / Homozygous type A blood, heterozygous Rh+, wavy hair

What are the genotypes of Mr. and Mrs. Jones?

What are the possible genotypes of the offspring? (May be easier to write blood type with Rh separate than hair texture).

To simplify, 3 separate punnett squares could be drawn and analyzed separately. One for blood type and then perform one for Rh factor separate. Then another for hair texture. Or you may use the space to work another way.

Write each person’s genotypes in the chart below:

Person / Blood Type / Rh Type / Hair Texture
Carl
Ray
Dale
Earl
Robert

Which men can be eliminated by these traits? Explain your reasoning for each man?

PART THREE: Epistasis

Now, we are just down to ______and ______. Let’s find out which one of them is the legitimate son.

(Note: The following is hypothetical):

In humans, D allows for 3-D vision and is dominant over d which allows for 2-D vision. Another gene determines whether an individual can see or not. Allele e allows individuals to see, but the mutant allele E prevents sight all together.

Mr. Jones / Heterozygous for vision type; Recessive for sight
Mrs. Jones / Heterozygous for vision type; Hybrid for sight
Carl / Unfortunately is blind (homozygous dominant) since he is homozygous dominant for 3-D
Ray / Sees in 2-D vision
Dale / Hybrid genotype for vision, but hybrid for sight
Earl / homozygous dominant for vision and can see
Robert / Homozygous dominant for both

What are the genotypes of Mr. and Mrs. Jones?

What are the possible genotypes of the offspring?

Write each person’s genotypes in the chart below:

Person / Genotype
Carl
Ray
Dale
Earl
Robert

SO, WHO GETS THE MONEY?

You can test yourself for astigmatism:

Stand about 20 feet away from the chart.
You can have astigmatism in one eye but not the other. Therefore you have to test one eye at a time. Close or hold on eye shut and view the chart (when done, repeat with other eye):

Do you see the chart clearly (3 individual lines for each number)?

NO ASTIGMATISM

Do you see some “grouping” of lines so it looks like a thicker black line, or all 3 lines grouped as one?

ASTIGMATISM