1. 1 in 1700 US Caucasian newborns have cystic fibrosis. C for normal is dominant over
c for cystic fibrosis.
a)Determine the frequency of each allele and each genotype in the population.
p =.976
q = .024
CC- Normal homozygous dominant = p2 = 95.3%
Cc -carriers of cystic fibrosis = 2pq = 4.68%
How many of the 1700 of the population are homozygous Normal? 1620.1
7. How many of the 1700 in the population are heterozygous (carrier)? 79.6
1. When counting the phenotypes in a population why is cc the most significant?
2. Albinism is a rare genetically inherited trait that is only expressed in the phenotype of
homozygous recessive individuals (aa). The most characteristic symptom is a marked
deficiency in the skin and hair pigment melanin. This condition can occur among any
human group as well as among other animal species. The average human frequency of
albinism in North America is only about 1 in 20,000.
a) Determine the frequency of each allele and each genotype in the population.
q = .007
p = .993
p² = predicted frequency of homozygous dominant individuals = .986 =
98.6%
2pq = predicted frequency of heterozygous individuals = .014 = 1.4%
q² = predicted frequency of homozygous recessive individuals (the albinos)
= .00005 = .005%
2. If 9% 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?
q = .3
p= .7
2pq = 42%
3. This is a classic data set on wing coloration in the scarlet tiger moth (Panaxia
dominula). Coloration in this species had been previously shown to behave as a singlelocus, two-allele system with incomplete dominance. Data for 1612 individuals are given
below:
White-spotted (AA) = 1469, Intermediate = (Aa) = 138, Little spotting (aa) = 5
Calculate the following frequencies:
A = 95.4%
a = 4.6 %
AA = 91%
Aa = 8.7%
aa = 0.003%
4. After graduation, you and 19 friends build a raft, sail to a deserted island, and start a
new population, totally isolated from the world. Two of your friends carry (that is, are
heterozygous for) the recessive cystic fibrosis allele (c), which in homozygotes causes
cystic fibrosis.
A. Assuming that the frequency of this allele does not change as the population grows
(Hardy-Weinberg Equilibrium), what will be the instance of cystic fibrosis on your
island?
2/40 alleles are c = q = .05
cc or q2 = .052 = .0025 or .25%
B. Cystic fibrosis births on the island are how many times greater than the original
mainland. The frequency of births on the mainland is .059%.
]
0.25/0.59 = ~4 times greater