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CP Biology

Face/Head Variation Lab (Baby Lab)

Why are even closely related siblings different both in genotype and phenotype? They differ because the variety of traits in a human population is very large and reproduction continually creates new combinations of traits.

What traits would your baby have at age sixteen if both you and a classmate (your make-believe spouse) are heterozygous for each trait listed in the following pages? Illustrate how inherited traits are determined by chance with the following simulation. As you proceed with this simulation, keep in mind that actual inheritance is much more complicated than this exercise implies, and that geneticists do not fully understand the process.

Procedure

1. Pair up into make-believe sets of parents. 2. Both parents, you and your partner, record your names on the data sheet.

3. On the data sheet, list the genotypes and phenotypes for each trait that you determine as you go along.

4. To determine the genotype for each trait, flip a coin (one each partner).

• “Heads” indicates that the parent flipping the coin contributes the dominant allele to the offspring (represent with a capital letter).

• “Tails” indicates that the parent flipping the coin contributes the recessive allele to the offspring (represent with a lower-case letter).

5. Flip for the head shape. • From the two large drawings provided, choose the face shape that represents the genotype you

determined from the information below. • Fill in the phenotypes on the head shape as you determine the genotype for each trait.

Guide for Determining Individual Traits

Sex. Determine the sex and name the child. (Only the “father” flips because he determines the baby’s sex). The mother donates an X.

Girl (X) Boy(Y)

Hair Color Dark color is dominant over light. At least four gene pairs are involved in determining hair color. Use the same procedure as for skin and eye color and please add another column to the chart, if necessary.

Face Shape See separate pages for enlarged handouts and choose on as follows:

Round (RR, Rr) Square (rr)

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DATA SHEET

Parents’ Name ____________________________and _____ _____________________________

Child’s Name_______________________________________ Sex_______________________

TRAIT Gene(s) from

Mother Gene(s) from

Father Genotype Phenotype

Face shape

Chin shape (I)

Chin shape (II)

Cleft chin

Skin color

Hair type

Widow’s Peak

Eyebrows (I)

Eyebrows (II)

Eyebrows color

Eyes/distance apart

Eyes-size

Eyes-shape

Eyes-slantedness

Eyelashes

Eye color

Mouth size

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Lips

Lips/Protruding

Dimples

Nose size

Nose shape

Nostril shape

Earlobe Attachment

Freckles on checks

Hair color