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BIOLOGY 101 Week 7 Experiment Answer Sheet
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BIOLOGY 101 Week 7 Experiment Answer Sheet
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WEEK 7 EXPERIMENT ANSWER SHEETPlease submit to the Week 7 Experiment dropbox no later than Sunday midnight.
SUMMARY OF ACTIVITIES FOR WEEK 7 EXPERIMENT ASSIGNMENT
Experiment 7 Exercise 1 – Evolutionary Change without Natural Selection
Experiment 7 Exercise 2 – Evolutionary Change with Natural Selection
Experiment 7 Exercise 3 – Evolution and Genetic Drift
Before starting, be sure you have read over the information in the Week 7 Experiment Introduction.
Materials Needed
For the first two exercises you will need the following:
50 red M&Ms and 50 green M&Ms or 50 each of two items that are distinguishable by color but
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are similar in size and texture (e.g., dimes and pennies, two different color beads).
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Four containers large enough to hold the above items.
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Experiment 7 Exercise 1: Evolutionary Change without Natural Selection
In this first exercise, we are going to look for evidence of evolutionary change in a population in the
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absence of natural selection by looking at the change in allele frequencies over time in a simulated
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population. We will start with a population of 50 individuals in which there are two alternate alleles (H
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and h) in equal proportions (each at a frequency of 0.5 or 50%). Individuals have the possible
genotypes: HH, Hh or hh. These two alleles do not offer any selective advantage, so neither is selected
for or against, meaning they are neutral. We will record the frequency of these alleles over 10
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generations. Prior to advancing on to the next generation, six alleles (= three individuals) will be
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removed at random.
Before you begin, answer the following:
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Question
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1. What is your prediction as to what will happen to the frequencies (note that this is different
than the number) of these two alleles over 10 generations? Word your prediction as an “if-
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then” statement based on the experiment design. (1 pts).
Updated October 2013
This study source was downloaded by 100000805705997 from CourseHero.com on 11-03-2021 21:22:30 GMT -05:00
https://www.coursehero.com/file/33031475/Week-7-Experiment-Answer-Sheetdoc/
, Procedure:
A. Let 50 M&M's of one color (i.e. red) represent the dominant allele (H) and 50 M&M's of
another color (i.e. green) represent the recessive allele (h).
B. Let one container represent the Habitat where random mating occurs. Place all of the M&Ms
(or other items) into this container. This is your starting gene pool of your “parent” population
or Generation 0.
C. Label the other three containers HH for homozygous dominant individuals, Hh for heterozygous
individuals and hh for the homozygous recessive individuals. Notice that individuals have two
alleles.
D. Mix up your Habitat well and without looking, select two items (alleles) at a time; these two
alleles represent a single individual. On a piece of paper, keep track of the genotypes of the
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individuals withdrawn. For instance, if you draw one red and one green M&M, that counts
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towards "Number of Hh individuals." If you draw two red M&Ms, that counts towards "Number
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of HH individuals" and so on.
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E. Continue drawing pairs and recording the results until all items (alleles) have been withdrawn
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and sorted. Be sure to place the “offspring” into the appropriate dish: HH, Hh, or hh. Note that
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the total number of individuals will be half the total number of items because each individual
requires two alleles, so you will have 50 offspring (but 100 alleles). Record the number of HH,
Hh and hh individuals drawn for Generation 1 in Table 1 below.
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F. Next count (or calculate) the total number of H and the total number of h alleles for the first
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generation and record the number in Table 1 below in the columns labeled "Number of H
Alleles" and "Number of h Alleles."
G. Add up the total number of H alleles and h alleles for the first generation and record this
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number in the column labeled "Total Number of Alleles." If you did everything correct, you
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should still have 50 H alleles and 50 h alleles. This has already been entered for you in the Table
below for Generation 1.
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H. Combine the HH, Hh and hh individuals back into the Habitat container and mix well. Randomly
remove three pairs of alleles (= three individuals, six items) and set them aside.
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I. Repeat steps D through H to obtain Generations 2 through 10. Remember to randomly remove
three pairs of alleles each time. Because I know that each generation will have six fewer alleles,
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I have also entered the total number of alleles in the Table below. Be sure that is the number
your alleles add up to!
Here is a photograph of this process after six generations. The sixth generation has been distributed
into the HH, Hh and hh containers. Note that dimes and pennies have been used.
Updated October 2013
This study source was downloaded by 100000805705997 from CourseHero.com on 11-03-2021 21:22:30 GMT -05:00
https://www.coursehero.com/file/33031475/Week-7-Experiment-Answer-Sheetdoc/
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