Download The Fishy Frequencies Lab

The Fishy Frequencies Activity: HWB Lab
The Hardy-Weinberg Principle states that allele frequencies in a population
will remain fairly constant unless one or more economic factors cause those
frequencies to change. The situation in which allele frequencies remain
constant is called “genetic equilibrium”. To measure allelic frequencies, five conditions are required to hold steady the
dynamic tendencies of alleles and measure their values from generation to generation. If the 5 assumptions are “in
place” we can calculate the allele frequencies at “generation X” and then after the population breeds, re-calculate the
allele frequencies “generation Y” and compare those same allele’s values
In this lab you will use little fishy crackers to help further your understanding of natural selection as it relates to genetics
and gene frequencies in evolution and how to quantify and calculate allele frequencies thus, mathematically measuring
evolutionary process.
Here are the details:
1. The little fish in this study are the natural prey of the terrible fish eating sharks—YOU!
2. The fish come with two color – related phenotypes, gold, and any other color you have:
a.
Gold is a recessive trait (f); these fish happen to taste yummy and are easy to catch.
b. Anything other than the standard gold is a dominant trait (F); these fish aren’t as yummy, in fact are
bitter tasting and are sneaky and are more difficult to catch.
3. You, the terrible fish eating sharks, much prefer to eat the yummy gold fish; you eat ONLY gold fish unless none
are available in which case you resort to eating bitter, yucky colored fish in order to stay alive.
4. New fish are born every “year” which occurs after a period of eating. (How convenient) The birth rate equals
one baby for each one eaten. Therefore, once data is recorded, add back in 3 babies from your ocean without
looking!
5. Since the gold trait is recessive, the gold fish are homozygous recessive (ff). Because the colored trait is
dominant, the colored fish are either homozygous or heterozygous dominant (FF or Ff).
Procedure
1. Randomly obtain a population of 10 fish from your “ocean” container. DO NOT LOOK!
2. Count gold and colored fish and record in your data table 1, you will calculate frequencies later.
3. Eat 3 gold fish; if you do not have 3 gold fish, fill in the missing number by eating colored fish.
4. Add 3 fish from the “ocean” (i.e., one fish for each one that died) by randomly selecting 3 new fish from your
“ocean”. Be sure to keep things random!
5. Now record the number of gold and colored fish present in generation 2.
6. Again eat 3 fish, all GOLD if possible and add 3 randomly selected fish from the ocean to add back in. Count
and record as generation 3.
7. Repeat the steps above in order to gather a total of five generations worth of data.
8. Based on your counts, compute the gene frequencies based on the Hardy-Weinberg equation to complete data
table 2 below.
9. After you’re done with your calculations and graphing, move on to the analysis questions below.
DATA TABLE 1
Generation
# of Gold Fish
# of Colored fish
Percent of Gold fish:
# of gold fish divided
by total number of
fish (10)
Percent of Colored
fish: # of colored fish
divided by total
number of fish (10)
1
2
3
4
5
1.
Using the information from the data table above, create complete line graph to show how your population
changed over time. Review: Dependent variable is ___________________ and is placed on the ____________
axis. And the Independent variable is ____________________ and is placed on the ___________ axis. Don’t
forget a title and labels!
2.
Now use your numbers data to calculate the frequencies of the alleles for color F or f each generation by
completing the data table:
DATA TABLE 2
generation
q2
q
p
p2
2pq
1
2
3
4
5
Analysis:
1. What are the 5 HWB assumptions?
2. Why are these assumptions placed?
3. According to the Hardy-Weinberg Equilibrium, what economic conditions would have to exist for the gene
frequencies in a population’s gene pool to stay the same over time?
4. Why is it important to collect data for multiple generations?
5. Explain which phenotype of the fish is NOT a favorable adaptation to the fish. Why is this?
6. Overall, what happened to the overall genotypic frequencies from generation 1 to generation 5?
7. What process is occurring when there is a large change in allelic frequencies over a period of time?
8. What would happen if it were more advantageous to be heterozygous (Ff)? Explain.
9. What happens to the recessive gene frequency over successive generations if ff is deadly?
10. Why doesn’t the recessive gene disappear from the population even in the face of such selective pressure?
11. So even if all the gold fish were eaten, is there a way to get gold colored fish back into the population? Explain
12. What is polymorphic in the fish population?
13. Is the fish’s color a Mendelian or non-Mendelian inheritance pattern? How do you know?
14. The allele for the ability to roll one’s tongue is dominant over the allele for the lack of this ability. In a
population of 1000 individuals, 360 show the recessive phenotype. How many individuals would you expect
to be homozygous dominant and heterozygous for this trait?
15. Could HWB frequency values of alleles be used to construct a cladogram? Why or why not?
16. Students counting beans collected this data for bean coloration, therefore what is the number of individuals for
each genotype? (The pop size is 2000 beans)
And remember the relative frequencies of the above values must = 1