Ecology – Biology 4250
Hardy-Weinberg Problems
SHOW ALL YOUR WORK ! ! ! Round answers to the nearest two significant digits
past the
decimal point. Unless otherwise specified, assume populations are in a
fictitious H-W equilibrium.
30 points total.
1. In a population with 2 alleles for a particular locus (D and d), the
frequency of the D allele is 0.64.
(4 pts.)
a) What is the frequency of the d allele?
b) What is the frequency of homozygous dominant individuals in the population?
c) What is the frequency of homozygous recessive individuals in the population?
d) What is the frequency of heterozygotes in the population?
2. Green elephants result from the cross between blue elephants and yellow
elephants. In a population
of elephants, 187 are blue, 927 are green and 533 are yellow. Could it be said
that the population is in
genetic (HW) equilibrium? If not, who seems to have a selective advantage? Can
you give a reasonable
explanation as to why that (those) particular color(s) would be selected for? (9 pts.)
3. In a population that is in Hardy-Weinberg equilibrium, 20% of the individuals
exhibit the recessive trait (ss).
(2 pts.)
a) What is the frequency of the dominant allele (S) in the population?
b) What percent of the population possesses the dominant allele (S)?
4. The frequency of children homozygous for a recessive lethal allele is about
1/25,000. What proportion
of the population (assuming equilibrium) are carriers of the lethal allele? (2
pts.)
5. Coat color in sheep is determined by a single gene. Allele B, for white wool,
is dominant over allele b,
for black wool. We have followed a population of sheep for two years. Below are
the statistics we have
compiled. (8 pts.)
Year 1
Year 2
White sheep
564
497
Black sheep
157
193
Total # of
721
690
a) Determine the frequency of both alleles (B & b) in year 1.
b) Determine the frequency of both alleles (B & b) in year 2.
c) Is this population in Hardy-Weinberg equilibrium? Explain why or why not.
d) If the allelic frequencies for a particular gene in a population remain
constant from year to year,
what does this mean about the evolution of wool color in this population of
sheep?
6. The formation of methylmercaptan from ingested asparagus is a recessive
trait. To find out if
you are a methylmercaptan forming individual, simply eat a serving of asparagus
and wait
approximately 20 minutes before urinating. You will be able to detect a very
distinctive odor if
you have inherited the ability to form methylmercaptan. What percent of the
population would be
homozygous recessive for this trait if it is known that 32% are homozygous
dominant? Understand
that this trait has no known selective value. (2 pts.)
7. In a particular species of flower, C1 codes for red flowers, C2 codes for
white, with the heterozygous
individuals being pink.
a. If the frequency of pink individuals in the population was .5163, would you
be able to estimate the
frequencies of the individual alleles in the population? Why or why not?
b. If the frequency of red individuals in the population was .629, what would
the estimated frequency of
pink and white individuals be in this same population?
8. Suppose the number of red, pink and white individuals in another population
of flowers was 433, 396,
and 671 respectively.
a. Could this population be said to be in H-W equilibrium? SHOW YOUR WORK!
b. Which flowers could be said to be at an apparent selective advantage?