Purpose: To demonstrate the principles of Mendelian
genetics and sex determination, including the concepts of allele,
phenotype, genotype, dominant, recessive, codominant, homozygous and
heterozygous by creating a simulated baby.
Materials: Two pennies, art supplies, paper.
Procedure:
1) Working with a partner, determine the genotype of the baby by
flipping pennies. "Mom" flips one penny to choose an allele for her
egg and "Dad" flips the other to choose an allele for his sperm.
(Note that the gender of the baby is a special case and is determined
by dad alone. Boys are XY and girls are XX. Mom can give only an X
but dad can give either an X or a Y.)
2) Record the alleles which resulted from the coin flips, and put
"sperm and egg" together. (You cannot pick the traits you want; life
doesn't work that way!) Write down baby's genotype for each trait in
Table 1. Heads represents allele #1 and tails represents allele
#2.
3) Record the baby's phenotype in Table 1. Note: Dominant alleles
are written with an uppercase letter and recessive alleles are
written as lowercase letters. Dominant alleles mask the expression of
recessive ones. Co-dominant alleles are written as uppercase letters
with a subscript. Co-dominant alleles result in a phenotype that is
blended.
4) Repeat steps 1, 2, and 3 for all traits and then draw, color,
and name your creation. Remember that you are drawing a baby's face -
not a child's or an adult's (no tattoos, no mustaches, no pierced
ears, noses, etc., and not too much hair!)
Concluding Questions:
1. Why is the coin flip used to represent the selection of
alleles?
2. Define the following terms:
allele-
phenotype-
genotype-
dominant-
recessive-
codominant-
homozygous-
heterozygous-
chromosome-
locus-
gene-
Results:
Table 1: Check here indicating whether you are the mom
or the dad
and fill in the
data below.
