Download Genetic Probability Candy Lab:

Genetic Probability Candy Lab:
Gregor Mendel used mathematical analysis of garden pea plants to develop the laws of genetics.
In this investigation, you will mimic his experiments by studying traits carried on human
chromosomes. Recall that each sperm and egg cell carries only one gene for any trait and when
these cells fuse during fertilization, the result is a fertilized egg with two genes for one trait, one
from each parent.
Because the separation of homologous chromosomes during meiosis is a random event, the
particular allele that a gamete carries for any single trait cannot be predicted. Therefore, the
chromosome pair that an offspring receives for that trait cannot be known.
Using genetic information known about an offspring’s parents, however, the principles of
heredity can be applied to determine the offspring’s probable genetic inheritance. The simplest
and most reliable calculations can be made, using Punnett Squares, if the parental genotype is
known.
In this investigation you will examine chance genetic events to determine the probability of
specific outcomes.
Pre-Lab Vocabulary & Questions:
Definition
Example
1. Homozygous
2. Heterozygous
3. Genotype
4. Phenotype
Questions:
1. In a human almond–shaped eyes (E) are dominant to round-shaped eyes (e). What are the
Genotypic ratios and Phenotypic ratios if you cross two heterozygous individuals.
Genotypic ratio:
Phenotypic ratio:
Objective: The purpose of this lab is to see how accurate a punnett square is in predicting the
probability of an offspring’s outcomes.
Materials: (per lab group of 2 students)
50 M&M’s (approximately 1 bag)
50 Skittles (approximately 1 bag)
Two plastic cups or containers
Procedure:
1. Label one cup “male” and one container “female”.
2. Count out 25 M&M’s for each cup and 25 Skittles for each cup. (Each cup should now
have a mixture of M&M’s and Skittles.) Shake each container to make sure the candy is
evenly mixed up.
What is the genotype for the Male? _______________________________
What is the genotype for the Female? ______________________________
3. Choose for one person to be the “Male” with the male cup and the other to be the
“Female” with the female cup.
4. Gently shake each cup, close your eyes and select ONE candy from your cup. In this
activity, there will be two possible phenotypes for eye shape:
1. E = almond-shaped eyes (represented by M & M’s )
2. E = round-shaped eyes (represented by Skittles)
(HINT: both parents are heterozygous, have a mix of M&M’s and Skittles)
5. After both partners have selected one candy each from the cup, place a check in the data
table in the correct column of the genotype selected. (Ex. If you and your partner each
chose an M&M from each cup, you would check EE box for the first trial)
6. Return the selected candy to the original cup selected from.
7. Continue selecting one candy from each container and recording your selections in your
data table until you have complete 25 trials.
Results:
Data Table: Individual Partners
Trial #
EE
Ee
Data Table: Class
ee
GROUP NAME
EE
Ee
ee
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TOTALS
19
% OF EACH
GENOTYPE
20
21
22
23
24
NOTE: WHEN YOU DONE TOTALING YOUR INDIVIDUAL
RESULTS DATA, RECORD YOUR DATA ON THE CLASS DATA
CHART ON THE BOARD IN FRONT OF CLASS.
25
TOTAL
COPY ALL CLASS DATA ONTO YOUR DATA TABLE: CLASS.
Conclusion (Analysis):
1. Why is it important to conduct a large number of trials in an experiment?
2. Look at the genotypic ratio from your Punnett square cross. These are
PREDICTED outcomes. Compare these predicted outcomes to the ACTUAL
percentages from your class data table. Are the percentages the same? Why or Why
not?