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HWE Homework
Show all calculations (Homework without work shown will only be worth half credit)
Friday Recitations: Due Oct. 19 at the start of class
Wednesday Recitations: Due Oct. 24 at the start of class
You have the option to turn homework in through Blackboard or a hard copy at the beginning of class.
Blackboard is preferred, but I understand that it is sometimes easier to write out your work.
1. In a population of Linanthus parryae, a small annual plant of the Mojave desert, 78% of the flowers
are blue and the remainder are white. Given that the flower color is controlled by alternate alleles
at a single locus and the blue is dominant to white, answer the following questions.
i. Using B for the dominant allele and b for the recessive (white) alleles, what flower
color phenotypes correspond to the genotypes BB, Bb, and bb? (0.25pt)
ii. What is the frequency of the genotype bb? (0.75pt)
2. A very large population of randomly-mating laboratory mice contains 42% white mice. White
coloring is caused by the double recessive genotype, "aa". Calculate allelic and genotypic
frequencies for this population. (1 pt)
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3. The ability to taste PTC is due to a single dominate allele "T". You sampled 200 individuals in
biology, and determined that 155 could detect the bitter taste of PTC and 45 could not. Calculate
all of the potential frequencies. (1 pt)
4. Sickle-cell anemia is an interesting genetic disease. Normal homozygous individuals (SS) have
normal blood cells that are easily infected with the malaria parasite. Thus, many of these
individuals become very ill from the parasite and many die. Individuals homozygous for the sicklecell trait (ss) have red blood cells that readily collapse when deoxygenated. Although malaria
cannot grow in these red blood cells, individuals often die because of the genetic defect. However,
individuals with the heterozygous condition (Ss) have some sickling of red blood cells, but
generally not enough to cause mortality. In addition, malaria cannot survive well within these
"partially defective" red blood cells. Thus, heterozygotes tend to survive better than either of the
homozygous conditions. If 6% of an African population is born with a severe form of sickle-cell
anemia (ss), what percentage of the population will be more resistant to malaria because they are
heterozygous (Ss) for the sickle-cell gene? (2 pt)
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5. Phenylketonuria (PKU) is caused by homozygosity for a recessive allele and can cause a severe
form of mental retardation. This condition affects 1 in 10,000 newborn Caucasian children.
Calculate the frequency of all unaffected genotypes (assume the genotypes are in Hardy-Weinberg
equilibrium). (2 pt)
6. In humans, albinism is caused by a single gene in the recessive homozygous condition. In the
human population as a whole the frequency of albinos is about 1 in 20, 000. Assuming the
genotypes are in Hardy-Weinberg equilibrium, what is the frequency of carriers (unaffected) in the
population? (1 pt)
7. The Rh blood type response system is controlled by the D allele. The genotypes DD and Dd are
Rh+ (Rh positive); dd is Rh- (Rh negative). The Basque people from the border between France
and Spain have the highest d frequency in the Rh system so far reported. In one study of 500
individuals, 230 were found to be Rh+ and 270 Rh-. Calculate the frequencies of the D and d
alleles, the genotype frequencies, and the proportion of Rh+ individuals who are heterozygotes.
(Assume the genotypes are in Hardy-Weinberg equilibrium) (2 pt)
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8. A certain form of color blindness in humans is sex-linked. Assume that 2% of the males in a
population are color blind. What percentage of the females in this population is expected to be
color blind at Hardy-Weinberg equilibrium? What is the percentage of the other genotypes in
the female population? Explain your calculation! (Bonus 0.5 point)
*HINT*