Download Hardy-Weinberg Law Lab

Hardy-Weinberg Law Lab
Background: The Hardy-Weinberg Law, expressed as p² + 2pq + q²= 1, allows
the calculation of allele and genotype frequencies in a population. In this
investigation, you will determine allele and genotype frequencies for traits
observed in you and your classmates.
Objectives:
 Calculate the frequencies of the dominant and recessive alleles for
inherited traits.
 Compare the frequencies of two alleles with the frequencies of their
phenotypes.
Procedure:
1. From the class data on the board, fill in the first 2 columns on your data
table.
2. Calculate the fraction of individuals who are homozygous recessive for
the traits. Express this as a decimal value. Record on the data table
under q².
3. Determine the frequency of the dominant allele using the formula
p = 1 - q. Record your answers on the data table.
4. Calculate and record on your data table the frequencies of the
homozygous dominant (p²) and heterozygous (2pq) genotypes.
Analysis and Conclusions:
1. Is q, the frequency of the recessive allele, larger or smaller than the
frequency of people showing each recessive trait? Why?
2. If you tested 10,000 people, do you think genotype frequencies would be
the same as those in your class? Explain.
3. If all Hardy-Weinberg conditions were met, what would be the next
generation’s allele frequencies be?
4. Cystic fibrosis is a recessive, inherited disease whose victims die before
they can reproduce. Which Hardy-Weinberg condition would not be met
under these circumstances?
5. What do you think would happen to the frequency of cystic fibrosis
alleles over several generations?
6. In fact, the allele frequency for cystic fibrosis in the U.S. seems to be
constant over several generations. What could account for this?
7. Evolution is sometimes defined as a change in allele frequencies over
time. In respect to this lab, what does this mean?
Data table:
Trait
# with recessive
genotype
and phenotype
Total #
in class
q²
q
p
p²
2pq