Probability and Heredity

Purpose:
You will simulate Mendel’s experiments by substituting coins for plant characteristics. You will then compare what you had expected with what actually happened.

Supplies:
2 coins
data sheets (see at right)
pencil
paper
TOSS COMBINATION
Result Count Total
HH    
HT    
TT    

 


Flipping Coins
Work in a pair, one person flipping both coins at the same time. The other person records the outcome on the data table.
Repeat until you have four flips. Make a note of the ratio of toss combinations for HH:HT:TT.
 Falling Coins
Tails and Heads
Repeat until you have a total of 50 flips. Make a note of the ratio of toss combinations for HH:HT:TT.
Repeat until you have flipped a total of 100 times. Make a note of the ratio of toss combinations for HH:HT:TT.
 The 100th Flip


Results, Questions:
1. Which combination of heads and tails did you expect to occur most frequently? (HT) Was your prediction correct?

2. What is the expected ratio of toss combinations for HH:HT:TT? (1:2:1)

3. How did your actual ratio after 100 tosses compare with the expected ratio?

4. Were your actual results closer to the expected ratio after 4, 50, or 100 flips? (100)

Applications:
1. What biological processes are represented by flipping and pairing the two coins?


2. Apply the probabilities of a coin toss to that of two different alleles. How are the chances of getting two tails similar to getting a homozygous recessive genotype? (the percentages are the same)