# Classical Genetics - Probability Lab

Please find the questions in the attachment.

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? Predict the probability of the occurrence of a single event.

? Predict the probability of two independent events occurring at the same time.

? Apply Mendel's law to predict the occurrence of certain traits in the offspring of parents exhibiting particular traits.

? Apply the meaning of the term Standard Deviation to sampling techniques.

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Part I: Probability of the Occurrence of a Single Event

1. Toss a penny 20 times. Count how many times it lands head up and how many times it lands tails up. Write the totals under the observed column for 20 tosses in Table 1 below.

2. Using the law of probability, decide how many times out of 20 tosses you would expect heads to appear and how many times you would expect tails to appear. Write your answer in the expected column for 20 tosses in Table 1 below.

3. Calculate deviation by subtracting the expected number from the observed number. Record these in the deviation column for 20 tosses in Table 1 below. Make all numbers positive.

4. Repeat Step 1, but tossing the penny 30 times. Count how many times heads and tails appear. Record the observed numbers in the observed column for 30 tosses in Table 1.

5. Calculate the expected number of heads and tails and record them in the proper column in Table 1. Then calculate the deviates, and enter these in the proper column.

6. Repeat Step 1, tossing the penny 50 times. Keep track of the appearance of heads and tails. Record the observed numbers, expected numbers and deviations in the columns for 50 tosses in Table 1.

7. Calculate the standard deviation for each of the four sections above; 20, 30, 50 and total tosses. To calculate the standard deviation, first, subtract the expected from the observed, as done in Table 1 and then square this value. Divide this value by the number of events. Take the square root of this result. This is your standard deviation. Enter your results in Table 2.

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Part II: Probability of Independent Events Occurring Simultaneously

1. Toss two pennies 40 times simultaneously. Keep track of how many times heads-heads, heads-tails, tails-heads, and tails-tails occur. Count tails-heads and heads-tails together. Record the numbers for each combination in the observed column in Table 3 below.

2. Calculate the percent of the total that each combination (heads-heads, heads-tails/tails-heads, or tails-tails) occurred and record it in the proper column. To find the percent, divide each observed number by 40 and multiply by 100.

3. Using the law of probability, predict the expected outcomes of tossing two pennies. Record the expected numbers in the proper column in Table 3.

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Part III: Probability and Mendelian Genetics

1. Place a small piece of masking tape on each side of two pennies. On one penny write R on each side. On the other penny write r on each side.

2. Toss the pennies several times. What combination of genes always appears? Would the offspring with these genes be round or wrinkled?

3. Replace the old tape with new tape. On each penny, write R on one side and r on the other side.

4. Toss the coins simultaneously until all possible combinations of genes have appeared. What combinations of genes appear? For each of the combinations, would the offspring be round or wrinkled?

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#### Solution Preview

Part one.

The purpose of this assignment is to see what the difference in probability takes place when one looks at chance over a limited number of events. As the number of events increase, the observed difference between the observed and expected probability should become smaller. So if you toss a coin 20 times the standard deviation should be higher than when the coin is tossed 50 times. For example let's say you toss the coin 20, 30, ...

#### Solution Summary

The classical genetics of probability lab is examined. An application of the meaning of the term standard deviation to sampling techniques are examined.