Download HARDY WEINBERG EQUILIBRIUM

IB Biology 2 / IHS
Hardy-Weinberg Equilibrium: A Problem Set
Directions: Work out the answers to these problems in your journal. Please show all work & circle your answers.
1.
The following numbers of genotypes were collected from a population of the scarlet tiger moth, Callimorpha dominula:
52 BB, 40 Bb and 8 bb. Calculate the frequencies of the B and b alleles in this population.
2.
In the USA, about 16% of the population has Rh negative blood. (Recall that allele d for Rh negative blood is
recessive, while allele D for Rh positive blood is dominant. If the USA is in Hardy-Weinberg equilibrium (HWE) with
respect to Rh, how many Americans are Rh pos carriers of the Rh neg allele?
3.
The MN blood group system* is determined by a pair of codominant alleles, LM and LN. Homozygotes for the LM
allele have the M antigen on their red blood cells and are said to have "Type M" blood. Homozygotes for the L N allele
have the N antigen and are said to have "Type N" blood. Heterozygotes have both the M and N antigens on their red
blood cells and have type MN blood. If a population of 1,000 people is in HWE for MN blood groups and the frequency
of LM is 0.6, how many individuals of each blood type are expected?
*Humans rarely produce antibodies against M or N antigens; hence, this blood type is generally not of concern in blood transfusions.
Questions #4-6. Suppose that you wish to establish a breeding flock of chickens and you purchase 50
birds. 20 of your birds are normal, but 30 have "frizzled feathers." Frizzled fowl, or "frizzles," have thin,
brittle feathers that curl up instead of laying flat. The gene controlling feather type has two alleles, KN
and KF. KNKN homozygotes have normal feathers. KFKF homozygotes have frizzled feathers.
Heterozygotes have intermediate plumage.
4.
Your 50 chickens interbreed and make a flock. If HWE were attained among their offspring, what
allele frequencies and genotype frequencies would be expected?
5.
Suppose that the offspring actually produced by your starter flock consist of 32 normal, 86 intermediate, & 32 frizzled
birds. From these observed data, calculate the allele & genotype frequencies.
6.
Propose a hypothesis that might account for the difference between observed and expected frequencies.
OPTIONAL! Challenge yourself! In the USA, the frequencies of the ABO blood group alleles are estimated to be: 67% "O allele," 26% "A"
allele, and 7% "B" allele. What are the frequencies of the four blood (pheno)types " Type O," "Type A," "Type B" and "Type AB?" Assume
the USA population is in HWE for this trait.
Hints:
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Remember that two different genotypes give the "Type A" phenotype; the same is true for "Type B."
For a 3-allele gene, the H-W equation becomes (p + q + r) 2 = 1, where p, q & r are allele frequencies.