Download Polygenic Traits Lab

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Date ____________
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Polygenic Traits
Background: Polygenic traits are traits that are controlled by more than one gene, i.e. height,
weight, hair color, skin color (basically, anything that deals with size, shape and color). This allows
for a wide range of physical traits. For example, if height was controlled by one gene A and if AA=
6 feet and Aa = 5 feet 7 inches and aa= 5 feet, then people would be one of three different heights.
Since height is controlled by more than one gene, a wide range of heights is possible.
Part A: How can polygenic traits have many different outcomes?
Let’s suppose that our height was determined by 3 genes on different chromosomes. Therefore, you
will get 2 copies of each gene, 1 from your mom and 1 from your dad. So, you will end up with 6
copies of the gene. Your height will then be determined by how many of these 6 genes are dominant
and recessive. Here is a simulation:
1. Toss each of your six coins and record the results in Table 1 under Trial 1. (heads = dominant,
tails = recessive)
2. Continue to toss the coins for the other 9 trials, recording heads and tails.
3. In table 2, record how many times you got each combination of heads and tails in the Group
row.
4. Once all groups have recorded their results, copy the class’ results in your table in the Class
row.
5. Construct a bar graph from the class data. The number of heads and tails will go on the X axis
(the independent variable), while the number of times the situation occurred will go on the Y
axis (the dependent variable).
Data:
Table 1
Flip (Group)
1
2
3
4
5
6
7
8
9
10
Number of tails
Number of heads
Table 2
Flip Situation
Your Group’s Total
Class’ Total
0T6H
1T 5H
2T 4H
3T 3H
4T 2H
5T 1H
6T 0H
Use the following chart to answer the questions:
1.
Penny Situation
Height
O Tails and 6 Heads
6 feet 1 inch
1 Tail and 5 Heads
5 feet 11 inches
2 Tails and 4 Heads
5 feet 9 inches
3 Tails and 3 Heads
5 feet 7 inches
4 Tails and 2 Heads
5 feet 5 inches
5 Tails and 1 Head
5 feet 3 inches
6 Tails and 0 Heads
5 feet 1 inch
If a male is 5 feet 9 inches tall, it means that he has 4 dominant genes and 2 recessive. He will only give 3
of these genes to his child. What are the possible combinations of genes that he can give?
2.
A father has 1 dominant gene and 5 recessive. How many dominant genes would an offspring have
gotten from its mother if they got the dominant gene from the dad and ended up being 5 feet 9
inches?
3. The male is 5 feet 7 inches and the female is 5 feet 5 inches. Is it possible for them to give their child
the necessary genes so the child can be 5 feet 11 inches tall?
4. Describe the shape of the graph that you created.
5. Why do you think the graph is small at the ends and large in the middle?
6. What do you think would happen to the chart above if more than 3 gene pairs controlled height?
7. Explain how polygenic traits affect the number of phenotypes of a particular trait.
8. Explain how some children can become taller than both of their parents?
9.
Infer how a trait that is polygenic has advantages over a trait that is controlled by just one gene.
Part 2: How do polygenic traits get passed from one generation to the next?
Follow the directions for “The Polygenic Pedigree Challenge”
Questions:
1.
The grandfather in this family was a “high risk” individual. How many of his children were
either medium or high risk individuals?
2.
How many of his grandchildren were either medium or high risk individuals?
3.
Did the number of “medium risk and “high risk” individuals decrease or increase over the
second and third generations?
4. Why do you think you saw an increase/decrease in #3?
5. Heart disease is not only caused by genes, it is also caused by environmental factors.
Environmental factors could be behaviors, lifestyle, or exposure to factors in the surrounding
environment. What are some environmental factors that might cause heart disease?
6. In this activity you were able to label family members as having a low, medium or high risk of
developing heart disease. In reality, do you think it might be difficult to predict an
individual’s risk of developing heart disease? Why?
7. If a parent is diagnosed with heart disease, does that mean the children will have it also?
Explain your answer?
8. How is it possible for a child to be a lower or higher risk of heart disease based on the genes
of the parents?
9. How do you think the chances of getting a disease that is controlled by just one gene compare
to getting a disease that is controlled by more than one disease?