Download Gene Combo - Township Site MSDPT

Name _____________________________________________
Date_______________
Gene Combo
Key Words: Allele, Dominant Model, Probability, Random
Getting Started:
1. What conclusions were you able to draw by the end of Activity 58, “Creature Features?” How many
genes for the tail-color characteristic do you think each critter has?
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2. In this activity, you will investigate a model for the behavior of genes that assumes that each parent
has two versions of the gene for tail color and that only one version from each parent is transferred
to each offspring. An allele is a version of a gene. In this activity, tail color is determined by two
different alleles; one provides information resulting in a blue tail and the other provides
information resulting in an orange tail. A coin-tossing simulation will be used to model a random
process for determining which of the two alleles a parent gives an offspring.
3. The chances of picking an ace of hearts from a deck of cards is 1 out of 52. This is the probability of
choosing that card. It is a random chance that the ace of hearts will be chosen. An example of a nonrandom probability is the result of a sporting event. If you ask who will win the next big football
game, the chance is not random; instead, the outcome will depend at least partially on the
preparation, talent, and ultimate performance of the rival teams.
4. What are the chances that a coin toss will result in heads (vs. tails)?
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5. Is this a random or non-random probability? Explain.
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6. Read the introduction and Challenge for Activity 59, “Gene Combo” in your Student Book.
IALS Genetics: Activity 59
Name _____________________________________________
Date_______________
Procedure:
1. In your groups of 3-4 students, divide into two pairs. Each pair should complete steps 2-5. If you are
working on this activity alone, you will need to represent both Ocean and Lucy.
2. Decide who will toss a penny to represent Ocean; the other person will toss a penny to represent
Lucy. The outcome of each coin toss determines the tail-color gene each parent passes on to each
critter pup.
3. Each person in your pair will toss a penny. For each toss, each partner should:
 Hold a penny in cupped hands.
 Shake it to the count of ten.
 Allow it to drop from a height of about 20-40 cm (8-16 inches) onto a table. Leave the pennies
on the table until you have completed Step 4.
4. Work with your partner to fill in the first row of Student Sheet 59.1, “Gene Combo Results,” which is
attached to this packet. Use the symbols below to keep track of the genes:
T = blue tail gene
t = orange tail gene
(You could use any letter you like, but T and t can remind you of “tail color.” To make your gene
symbols easy to tell apart we suggest you always underline the uppercase letter of the pair.)
For example, if Ocean’s coin toss results in heads (T), and Lucy’s coin toss results in tails (t), your first
entry will be:
Gene Combo Results
Offspring
Ocean’s
Contribution
(T or t?)
Lucy’s
Contribution
(T or t?)
Offspring’s
Genes (TT, Tt, tT,
tt?)
1
T
t
Tt
Offspring’s Tail
Color
(blue or
orange?)
blue
5. Repeat Steps 2-4 until you have filled in every row of the table.
Remember:
TT = blue tail
Tt, tT = blue tail
Tt = orange tail
6. Your classmates now worked in their groups of four to summarize their results. You will
summarize just your and your partner’s results by preparing a simple table. Include the total
number of times you got each gene combo (TT, Tt, tT, tt?) and the number of times you got each tail
color (blue or orange).
IALS Genetics: Activity 59
Name _____________________________________________
Date_______________
7. When you return to class, you will report your results to your teacher.
8. Add another row to your table to record the class data. If absent, this is a sample class data is
shown below.
Blue tails = 460
ABSENT ONLY
Orange Tails = 160
Analysis Questions:
1. What is the ratio of blue-tailed to orange-tailed critter pups? Use the class data to answer this
question:
a. Divide the number of blue-tailed offspring by the number of orange-tailed offspring.
Ratio of tail colors = number of blue-tailed offspring
number of orange-tailed offspring
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b. Round this value to the nearest whole number. Then express it as a ratio by writing it like
this:
__________________ : 1
(whole number)
c. Express this ratio as a pair of fractions, so that you can use them to complete the following
sentence:
“About _____________ of the offspring have blue tails, and about _________________ of the offspring
have orange tails.”
d. Explain why the class obtained such a large ratio. For example, why isn’t the ratio of blue to
orange tails 1:1, that is, ½ blue and ½ orange?
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2. You and your partner are about to toss two coins 100 times. Predict about how many times the
outcome would be:
a. heads-heads
b. heads-tails
c. tails-heads
d. tails-tails
IALS Genetics: Activity 59
Name _____________________________________________
Date_______________
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3. How sure are you that you will get exactly the results you predicted for Question 2? Explain your
answer.
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4. Look back at Activity 58, “Creature Features.” Do the results of the coin-tossing model match the
Generation Three critter data? Explain.
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5. What are the advantages and disadvantages of using coin tosses in a model for how genes are
passed from parents to offspring? Explain.
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6. Review the rules of genetics that the class developed in the last activity. Which ones make this
model work?
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IALS Genetics: Activity 59
Name _____________________________________________
Date_______________
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7. Write your own definition of the phrase dominant trait as it is used in genetics. Hint: Does it mean
that every time any pair of critters mates, most of the offspring will have blue tails? Why or why
not?
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IALS Genetics: Activity 59
Name _____________________________________________
IALS Genetics: Activity 59
Date_______________