Pedigrees Using M&Ms
Pedigree charts are often used to document the movement of traits through generations. It is
particularly useful in the practice of genetic counseling as geneticists talk to families about their
risks of producing offspring that have recessive or dominant disorders that have been present
within their family lineage. Below are common symbols used in creating and documenting
pedigrees.
Materials:
M&Ms
Minis…autosomes: red, yellow, brown, blue,
sex chromosomes: green, orange,
Large…Blood cells: white, red, dark pink, light pink
2 cups
Data:
Create your pedigree chart with the correct symbols as noted above. Use a color pencil to
note the genes present in each individual. Label each individual’s characteristics.
Interpretation of M&M traits:
Sex
Green = Y.. male always starts with a Y & an X
Orange = X.. female always starts with 2 Xs
Hair/skin/eyes (Brown/Yellow/Red/Blue)
Skin color…
Dark skin at least 1 brown and no yellow present
Tan skin if at least 1 brown and 1 yellow present
Fair skin if no brown present and at least 1 yellow present
Albino if no brown or yellow present
Hair
Black hair if no yellow present but at least 1 brown
Brown hair if 1 brown present and at least one yellow or red
Blond hair if no brown present
Strawberry blond if no brown and a red and at least one yellow
Red if there is red but no brown or yellow
White if no brown, yellow, or red
Eyes
Brown eyes if 1 brown present
Blue if no brown or red but at least 1 blue present
Green if no brown but there is at least 1 blue and 1 red
Albino (red) if no brown or blue present
Blood type
IA
Red
IB
Dark pink
IO
light pink
Sickle cell trait white
IA IA and IA IO are both type A IA IB is IB IA are both type AB
IB IB and IB IO are both type B
IO IO is type O
Sickle cell disease ISIS (draw a line through this individual…died)
Prelab Questions:
1. Describe how each is related to the other. Allele, gene, chromosome.
2. How many autosomes and sex chromosomes are present in human cells.
3. Define the following traits:
a. Recessive
b. Dominant
c. Codominant
d. Sex-linked
4. What type of disease is sickle cell? Explain.
5. What type of trait is blood type?
M&M Procedure Notes:
I: Establish the Genotype of the Parent generation: (Get 2 cups to start)
Autosomes:
 Grab 2 of each M & M and place into one of the cups. Mix.
o Without looking remove 4 M & Ms and place into a second cup. This is the
Genotype of the P generation.
Blood Type:
 Without looking grab 2 M & Ms from the blood type jar to establish your blood type.
Place into the second cup.
 If you get 2 white, grab another and place one white back.
Sex chromosomes:
 Grab 2 orange if you’re a female or a green and an orange if you’re a male. Place into
the second cup.
Record the genotype and phenotype of your P generation in the Data section of your lab:
II: Mating:
1. Find someone of the opposite sex and MATE!
a. Each person takes 2 random autosomes from their mate to form the first offspring.
Record on your pedigree chart.
b. Each person reaches into the blood type/sex chromosome cup and grabs one of
each. Record on your pedigree chart
c. Reset to the P generation each mating:
i. Continue to mate until you have at least 1 female and one male.
ii. Record ALL offspring on your growing pedigree chart.
2. Next Generations (F1)
a. If you are a girl, assume the genotype of your first female offspring.
b. If you are a male, assume the genotype of your first male offspring.
c. Mate with a new partner per the procedure above:
3. Repeat step 2 for F2-F4
(after you are done please replace ALL M&Ms to the appropriate cups)
Post lab Questions:
1. What was the purpose of randomly removing 4 alleles in the development of the P
generation?
2. Why was it necessary to reset the parent alleles before each child is created? Why not
just use the remaining alleles to create the next offspring?
3. Were any 2 of the offspring from you matings identical? If so how many?
4. Why is it possible to have identical offspring for our 4 alleles but no 2 human individuals
are the same?
5. Over the 4 generations did the individuals become more similar or dissimilar to the
original P generation?
6. How common was it to have recessive traits expressed compared to dominant ones.
7. Make a class tally of individuals to find out
a. how many total carriers of sickle cell trait
b. how many individuals were born that had sickle cell disease
c. express these numbers as a percentage of the whole.
8. Do you think that these numbers represent a realistic view of America?
a. Do some research and justify your answer.