Biology 30 – Extra Practice
1.
2.
3.
4.
5.
A particular recessive trait was found in 300 out of 1200 people observed.
a. Calculate the allele frequencies for the recessive and dominant alleles. p = 0.50; q = 0.50
b. Calculate the percent of students that would be carriers of the allele for the recessive trait. 50%
c. Calculate how many of the 1200 students would be homozygous dominant genotype. 300
The recessive allele frequency for attached earlobes is 25% in a group of 2200 people.
a. Calculate the genotype frequencies.
homozygous dominant p2 = 0.5625 heterozygous 2pq = 0.375 homozygous recessive q2= 0.0625
b. Calculate how many people in the group have free (unattached) earlobes.
2062.5 = 2063 people
In a population of 250 squirrels, 85% have the dominant black fur colour and 15% have the recessive grey fur
colour. How many of the black squirrels are heterozygous?
118.64… = 119
Oculocutancous albinism (OCA) is an autosomal recessive genetic disorder. People affected with OCA have no
pigment in their eyes, skin or hair because they are unable to produce normal quantities of the pigment
melanin. The frequency of OCA in Northern Ireland is 1 in 10 000. What is the frequency of carriers of OCA in
the population of Northern Ireland?
0.02
In a randomly mating population of Drosophila, 4% of the flies have black bodies (an autosomal recessive trait)
and 96% have brown bodies. This population is assumed to be in Hardy-Weinberg Equilibrium. If a researcher
samples 10 000 Drosophila from this population, the number of flies expected to be homozygous dominant for
body colour is:
a. 9600
b. 6400
c. 3200
d. 400
Use this pedigree to answer the next two questions.
6. Based on the information above, the inheritance of the PKU allele is
a. Autosomal recessive
b. Sex-linked recessive
c. Autosomal dominant
d. Sex-linked dominant
7. If the individuals in this pedigree presented a distinct population, how many of the 21 people could be expected
to be heterozygous for PKU? 10.32… = 10
Use the following information to answer the next two questions.
Lactose intolerance can be genetically inherited as an autosomal recessive trait. An individual who is lactose
intolerant does not produce the lactose enzyme needed to break down lactose, the sugar present in milk. The
distribution of lactose intolerance for different groups of humans is given below.
Human Group
Individuals Examined
Lactose Intolerant Individuals
American Caucasians
245
29
Finns
134
24
Thai
134
131
Native Americans
24
24
8.
If lactose intolerance is inherited in an autosomal recessive mode, then the frequency of the lactose intolerance
allele in the Finn population is 0.42.
9. The hypothesis that all lactose intolerant individuals examined are homozygous recessive for the phenotype
could best be confirmed by:
a. asking additional individuals in each human group if they have difficulty digesting milk.
b. asking the same examined individuals included in this table if either parent has difficulty digesting milk.
c. testing individuals with lactose intolerance for the presence of two copies of a mutation in the gene
coding for lactase.
d. testing individuals without lactose intolerance for the absence of two copies of a mutation in the gene
coding for lactase.
10. A small religious group called the Dunkers emigrated from west Germany to the United States. The frequency of
blood Type A is 60% among the dunkers, compared to 45% in west Germany and 40% in the United States. The
high occurrence of blood type A among the Dunkers is most likely the result of
a. mutations
b. genetic drift
c. natural selection
d. bottleneck effect
11. Statements that may be associated with the Hardy-Weinberg Equilibrium.
1) Open population
2) Closed population
3) Non-random mating
4) Random mating
5) Low mutation rate
6) High mutation rate
7) Large population
8) Small population.
Which of the statements listed above are assumptions made in order for the Hardy-Weinberg equilibrium to be
valid? (Record your answer in ascending order). 2457
12. Many elk live in and around an 80km2 area that includes the Jasper town site in Alberta. If an epidemic disease
were to kill 90% of these elk, what would be the likely consequences?
a. The genetic variability in the population would increase.
b. The genetic variability in the population would decrease.
c. The mutation rate in genes for disease resistance would increase.
d. The population’s gene frequencies would return to pre-epidemic values through genetic drift.
Use the following information to answer the next two questions.
A high percentage of dogs have genetic defects. One example of an autosomal recessive genetic disorder is hip
dysplasia, a defect in the hip joints that can cripple a dog, which occurs in 60% of golden retrievers.
13. What is the frequency of the abnormal allele that causes hip dysplasia in golden retrievers? Round your answer
to the nearest hundredth. 0.77
14. The row that correctly shows the percent frequency of the homozygous recessive golden retrievers and the
percent frequency of heterozygotes in a population is
Frequency of homozygous recessive dogs (%)
Frequency of heterozygous dogs (%)
A
60
35
B
40
35
C
60
23
D
40
23
15. A community of Pima Indians in the American Southwest has a very high rate of diabetes in their adult
population. Of the population of adults over that age of 35, 42% to 66% develop diabetes. The recessive trait
that causes diabetes in this population is a distinct disadvantage to individuals whose diets are rich in
carbohydrates. If 42% of the population had diabetes, then the percentage of the population who are carries is
calculated to be 46 % (rounded to the nearest whole percent).