Download Activity 59 (answers)

Name:_______________________Date:_______________Period:_______Score:_____
Activity 59-Gene Combo
Background information on the coin toss model:

The outcome of a coin toss represents the one version of a tail color gene that is contained in the sex
cell contributed by the parent critter. “Heads” represent the blue version and “Tails” represents the
orange version

A future offspring critter receives a version of the tail color gene from each of its two parents when
fertilization occurs.

Each side of the coin represents one of the two versions of the tail color gene carried by each
generation 2 critter.

Blue tail (T) color is dominant over orange tail color (t). This means that if a critter has at least one
copy of the blue version of the gene, its tail is blue. A critter has an orange tail only if it has no blue
version of the tail color gene.

Genotype is the actual genetic information represented in your DNA, Phenotype is the expressed
characteristic (in this case, color).
Procedure: Read the procedure on page D-31 to D-32 #1-8 and complete the data table below.
Offspring
Oceans allele
contribution
(T or t)
Lucy’s allele
contribution
(T or t)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
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Offspring’s genotype
(TT, Tt, tT, tt)
Offspring’s
phenotype
(blue or orange)
Name:_______________________Date:_______________Period:_______Score:_____
Data Collection Analysis:
1. Now, add your results from “Offspring’s genotype” column and fill in the group “genotype data” below.
2. Add your results from Offspring’s phenotype data and fill in the “Group Phenotype data” below.
3. Participate in class collection of data and fill in the “class Phenotype Data” below.
Group genotype data
TT
Tt
tT
Group phenotype data
tt
Blue Tail
Orange Tail
Class Phenotype Data
Blue Tail
Orange Tail
Analysis1. According to the class data, what is the ratio of blue tailed to orange tailed critters? Express as a ratio
and as a fraction.
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
b. Round this value to the nearest whole number. Then express it as a ratio by writing it like this:
3:1
(whole number)
c. Express this ratio as a pair of fractions, so that you can use them to complete the following
sentence:
“About 3/4 of the offspring have blue tails, and about 1/4 of the offspring have orange
tails.”
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Name:_______________________Date:_______________Period:_______Score:_____
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.
3 of the 4 times you will get a BLUE result.
Blue is dominant, therefore, it will show up more.
NOTE: You get 1 allele from mom, one allele from dad,
therefore, 50% of your genes from mom, 50% from dad.
2.
You and your partner are about to toss two coins 100 times. Predict about how many times the outcome
will be:
a. Heads-Heads (TT)- 25%
NOTE: The same holds true, ¾
b. Heads-Tails (Tt)- 25%
would be BLUE, ¼ would be
c. Tails-Heads (tT)- 25%
orange.
d. Tails-Tails (tt)- 25%
3.
How sure are you that you will get exactly the results you predicted for Question 2? Explain your
answer.
You cannot be 100% sure.
Probability shows us how LIKELY something will be,
but it is not for certain.
(think of a family of 4 kids…are there 2 girls and
2 boys because you are either male or female? Likely not…)
4. Look back at Activity 58, Creature Features.” Do the results of the coin-tossing model match the
Generation Three critter data? Explain.
YES! We got a 3:1 ratio, which is what the 3rd generation
showed. NOTE: BECAUSE ¾ BLUE,
¼ ORANGE WHEN CROSSING Tt x Tt
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Name:_______________________Date:_______________Period:_______Score:_____
5. Now that you have learned a little bit about dominant traits, try and 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? _____________________________
NOTE: It depends on what the parent’s genotype is!
If a heterozygous pair mates, then yes, most will be blue.
Any other combination will result in different %.
6. Reflection:
What, if anything, needs clarification?
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