Evolution – 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.

1. In a population with 2 alleles for a particular locus (D and d), the frequency of the D allele is 0.91.

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. The fraggles are a population of mythical, mouselike creatures that live in underground tunnels and
chambers beneath a large vegetable garden that supplies their food. They can reproduce VERY quickly!
Of the 154 fraggles currently in this population, 93 have green fur and 61 have gray fur. Green fur is
controlled by a dominant allele F and gray fur by a recessive allele f.

a) What is the frequency of the gray allele f?

b) What is the frequency of the green allele F?

c) How many fraggles are heterozygous (Ff)?

d) How many fraggles are homozygous recessive (ff)?

e) How many fraggles are homozygous dominant (FF)?

3. One summer, a dust storm blankets the usually green garden of the fraggles in gray for a short period
of time. Under these conditions, the green fraggles become very visible to the Gorgs, monstrous beasts
who tend the gardens and try to kill the fraggles to protect their crops. The gray fraggles, however,
blend into the dusty background and find that they can easily steal radishes from the garden. How
might this event affect microevolution in this population of fraggles, at least temporarily? Remember,
the fraggles can reproduce very quickly!




4. In a population that is in Hardy-Weinberg equilibrium, 16% of the individuals exhibit the recessive
trait (ss).

a) What is the frequency of the dominant allele (S) in the population?

b) What percent of the population possesses the dominant allele (S)?

5. The frequency of children homozygous for a recessive lethal allele is about 1/25,000. What proportion
of the population are carriers of the lethal allele?

6. 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
                                            Year 1         Year 2

White sheep                             489             682

Black sheep                              128            176

Total number of individuals        617            858

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? 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?

7. 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 30% are homozygous dominant?

8. 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 .737, what would the estimated frequency of
pink and white individuals be in this same population?

c. There is a pollinator introduced into the population of flowers that prefers to visit white flowers
8 to 1 compared to red flowers, and visits red and pink flowers equally. Starting from the frequencies
in b. (above), and assuming all pollinated flowers participate equally in generating the next generation,
what would the frequencies of the C1 and C2 alleles be in the next generation?

9. Suppose the number of red, pink and white individuals in another population of flowers was 398, 789,
and 444 respectively. Could this population be said to be in H-W equilibrium? SHOW YOUR WORK!