Assignment: Variations on a Human Face

Follow the link to access this week's readings. Be sure to read each of the THREE sections. You can do so by hitting the "next topic" button located at the bottom of each screen.

http://anthro.palomar.edu/mendel/mendel_1.htm

After completing the three pages of readings, move to the following assignment.

Single Allele Traits

1. Flip a coin to determine the gender of the offspring, if the coin lands heads up, the offspring is female, if tails, then the offspring is male. What sex is your offspring?

2. For all coin tosses from now on, heads will represent the dominant allele and tails will represent the recessive allele. For each trait (hair, eye, skin, and all other traits on the chart), you will flip a coin to determine the GENOTYPE of your offspring. Flip the coin twice (once from each parent) for each pair of alleles.

Example: For the shape of the face, your partner tossed heads and you tosses tails. This means the offspring's genotype is Rr and the child will have a round face, so check that box. If you had both tossed tails, you would check the square-shaped face (rr) and if you had both tossed heads, you would have a round shaped face (RR)

3. Circle the box that represents your offspring's appearance, or PHENOTYPE, in the chart.

4. Type up your responses and submit your work as a word document.

Polygenic Traits - Hair, Eye, Skin

Some traits are controlled by more than two genes, such as hair color, eye color and skin color. For these traits you will need to perform a different procedure to determine your offspring's phenotype.

Hair color

Dark hair is dominant over light. To determine the color of the offspring's hair, assume there are two gene pairs involved (there are actually probably more than that, but for the purpose of this activity, let's not go crazy). Flip your coin first to determine the genotype of the first pair of alleles (AA, Aa, or aa). Now, flip the coins again to determine the genotype of the second pair of alleles (BB, Bb, or bb). Match the genotype you have to the hair color on the chart. Circle your offspring's hair color.

Eye Color

Dark eyes are dominant over light. To determine the color of the offspring's eyes, assume there are two gene pairs involved, one which codes for depositing pigment in the front of the iris, and one which codes for depositing pigment n the back of the iris. Determine the genotype of the first pair (AA, Aa, or aa) Then flip again to determine the genotype of the second pair (BB, Bb, or bb). Use the chart below to find out what eye color your offspring has and circle it.

Skin Color

Skin color is controlled by a lot of different genes that basically add together to determine how dark the skin is and variations in tone. To simulate how skin color might be determined. Flip a single coin 10 times. Each time the coin turns up heads, give your offspring a point. Add your points together. 10 points would be a very dark child and 1 point would be a very pale child. How many points does your child have?

Analysis and Conclusions (Please provide your written responses to the following questions.)

1. Begin your written assignment by offering the physical attributes of your child, based upon your coin tosses. Then answer the following questions.

2. How might it be possible for you to show a trait that neither parent demonstrates?

3. Which traits are co-dominant or incompletely dominant? (Traits that do not have a clear dominant or recessive characteristic, but rather, the heterozygous condition shows a "blending" or a "middle" condition)

4. Why did you have to flip the coin twice to determine hair and eye color?

5. Show the cross of a wavy haired person with a wavy haired person by diagraming a Punnett square.

6. You have large, almond shaped eyes and curly hair. You mate with a person that demonstrates straight hair and small eyes and ears. Does this information tell you anything about the personality of your future offspring? Why is this so? How did you reach your conclusion?

7. Tell me about three of your physical characteristics. Do your parents possess the same phenotypes? Are phenotypes always the same as genotypes, why?

8. Explain what you learned by completing this assignment. Be sure to use appropriate terms and concepts in your written summary.