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Vocab:
Allele
Phenotype
Genotype
Dominant
Recessive
Trait
Incomplete
dominance
Polygenic
inheritance
Includes:
 Teacher
Directions
 Background
Vocabulary
Notes
 Answer Key
Student
Lab Sheet
An NGSS-aligned lab that reinforces the concepts of
genetics and inheritance of traits with simple coin tosses
Teacher Directions:
Crazy Snowman Genetics is designed to reinforce the vocabulary in a DNA and genetics
unit. This lab is typically given after going over Punnett Squares and genetics vocab. I
have included some optional background vocabulary notes that you can use if needed.
Recommended time: 1 hour and 20 minutes total
 30 minutes for directions and coin tossing
 30 minutes to draw snowman
 20 minutes for conclusion questions
 20 minutes to review student responses and collect data on traits
Note: the drawing can easily be assigned as the homework portion
Materials needed: 1 coin/penny per student
Procedure:
1. Pass out the student copies and read the directions with the students.
Do one example together of the genotypes and phenotypes before handing each student a
penny/coin. Please see diagrams below for an example where I flipped a coin and got 1
heads and 1 tails.
I do the first trait with the
students where we determine if
the snowman will be made of 2
or 3 snowballs.
Since I got 1 heads and 1 tails I
write Ht in the box. I write H as
capital just to signify it’s the
dominant trait. I ask them what
I do, since I got one of each trait
from my parent snowmen. We
review how when a dominant
trait is present, it covers up the
recessive one. So then I write
the phenotype as the dominant
trait.
2. Have students begin flipping their coins. You may need to pause the class when they get
to the polygenic inheritance part. If students seem confused, go over an example of
these with them.
3. Once students have completed flipping their coin for each trait, collect the coins, and
they can begin drawing their snowman or working on the conclusion questions. I have also
had students build the snowmen out of cotton, tissue paper, popsickle sticks, construction
paper, glue, string, etc… If you have an extra day, this might be the route you want to
take as well.
4. I usually assign the drawing and conclusion questions for homework as I typically teach 50
minute periods. I also make the conclusion questions worth more points than the drawing,
but that is up to you.
5. When students arrive the next day, we set out our snowmen and collect data on how many
snowmen ended up with each trait. We usually only do a few before students notice a
pattern that about 75 percent of the snowmen for every trait has the dominant
phenotype shown. 25 percent have the recessive trait.
6. It is very important to review student thoughts to conclusion questions 3 and 4 as this
lab is intentionally not always how genetics works. Some students at the middle school
level will have some good thoughts with this where others may struggle. Students who
have a deep understanding of genetics will comment on how for every coin flip we are
assuming that each parent was heterozygous. This means that every coin has an equal
chance of getting heads or tails. In real life a parent might be heterozygous dominant and
only be able to give the offspring a dominant allele. Pretty much no matter what, that
snowman offspring will never have the recessive trait. I
usually wait for a student to share this and then we draw a
Punnett square that represents the scenario we were doing
for these trials and then students start to have an Ah-ha
moment when they realize why 75 % of their snowmen had
the dominant traits. This is what I usually draw, but I
usually stick with H or t for the dominant and recessive for
this lab.
NGSS standards covered:
MS-LS3-2. Develop and use a model to describe why asexual reproduction results in offspring
with identical genetic information and sexual reproduction results in offspring with genetic
variation. [Clarification Statement: Emphasis is on using models such as Punnett squares,
diagrams, and simulations to describe the cause and effect relationship of gene transmission
from parent(s) to offspring and resulting genetic variation.]
Crazy Snowman Genetics Lab
Name
___________________
Directions:
 You are going to design your own snowman for this activity, but you cannot choose any
of the traits that your snowman is going to get. It will be left up to chance just like in
real life. For the first part of this activity you will flip a coin two times to determine
what type of trait your snowman will inherit. We flip the coin twice because it shows an
allele coming from each parent.
 If you get heads on a coin toss, that will be the dominant allele getting passed down
 If you get a tails, that is like a recessive allele getting passed down
 Once you get your two alleles from you coin flip, write them in the genotype column. Use
a capital H for the (dominant) Heads and a lowercase t for the (recessive) tails.
 Then use your knowledge of how traits work to determine whether that genotype will
show the dominant or recessive phenotype/physical trait.
 Rules:
1. No cheating – do honest flips – you cannot pick your traits
2. Control your coin to your area. Don’t let it hit the ceiling or leave your area.
Part 1
# of Dominant
Flips Trait
2
made up of 3 snowballs
2
Big carrot nose
2
Coal for mouth, belly,
and eyes
2
Scarf
2
Fat
Top hat
2
Sticks for arms
2
white snow
2
No legs
2
Normal vision
Recessive
The genotype The phenotype
(Ht, HH, or tt) (Physical trait)
Trait
Made up of 2 snowballs
Banana nose
Buttons for mouth, belly
and eyes
Bling-bling necklace
Incredibly fat
Baseball cap
Spotted cow arms
yellow snow
Monkey legs
Color blindness (show
by making eyes different colors)
2
2
2
2
No top
No pants
Buck teeth
Got into a snowball fight
(draw band aids, bruises,
cuts, etc…)
Sweater vest
Grass skirt
Braces
Has rabies (foaming at
the mouth)
Part 2: Remember that some traits use multiple genes working together to produce the trait.
This is called polygenic inheritance. For the following flips you are going to flip more than 2
times to represent some of these traits. There is also another type of inheritance where the
traits are sort of “mixed” together. This is called incomplete dominance. In order to get the
incomplete dominant trait, you must get exactly 50% of your flips to be heads and tails.
# of
Flips
4
4
4
6
6
8
Dominant
(At least 1 H)
Mustache
Smooth snow
Holding a broom
No glasses
Human ears
Lots of hair
Incomplete Dominant
Trait (Exactly 50%)
Goatee
Lumpy head
Holding a trident
A monocle (1 lens)
Bear ears
Balding in some areas
Recessive
Genotype
(all tails)
Beard and mustache
Lumpy all over
Holding a spear
BIG 1970’s glasses
Mickey mouse ears
Completely bald
Phenotype
PART 3: Conclusion
1. What did each coin flip represent?
2. Which traits seemed more common or more likely for the snowman to get:
Recessive or Dominant traits? Why is that?
3. What in this activity is accurate with how genetics really works?
4. What was inaccurate about flipping a coin compared to how genetics works?
Hint- think about what everyone’s coin had on each side.
Name
PART 4
___________________
Now that you have completed the genotypes and phenotypes of your snowman, you must
accurately display the phenotypes of your snowman with a well-drawn picture! Draw it big and
colorful.
Answer Key
Genetics notes
?s/main ideas
Essential Question: How are traits inherited?
An __allele_________ is the different forms of a trait a
gene might have.
B or b
A Dominant trait_ is one that covers up another trait
completely. It is always shown as capital letters.
B
A ___Recessive_ trait is one that seems to disappear. It is
always shown as lower case letters.
b
_Homozygous_ is when two alleles are the same.
BB or
bb
_ Heterozygous is when two alleles are different.
Bb
__genotypes______________ are the possible allele
combinations.
__Phenotypes__ are the possible physical traits
one sees.
BB, Bb, or bb
Brown hair or
blonde hair
__Punnett Square is a tool used to predict what
traits offspring will have.
Sometimes one trait cannot dominate over another trait completely.
The trait will mix with the other trait. This is called __incomplete__
dominance. Example: _red flower + white flower = pink flower___
Human blood type has _multiple alleles_ that can code for the
offspring. A, B, and O can make AB, A, B, AO, BO, and OO. The O
is recessive to both the A and B.
__polygenic____ inheritance__ occurs when a group of gene pairs
act together to produce a trait. For example, ___eye color___,
height, and skin use multiple gene pairs.
Summary: Answer
your essential
question by
answering all of
your chunking ?s
Genetics notes
?s/main ideas
EQ: How are traits inherited?
An ___________ is the different forms of a trait a gene
might have.
A ___________ _________ is one that covers up another
trait completely. It is always shown as capital letters.
A _____________ trait is one that seems to disappear. It is
always shown as lower case letters.
_______________ is when two alleles are the same.
________________ is when two alleles are different.
________________ are the possible allele
combinations.
_______________ are the possible physical traits
one sees.
____________ ________ is a tool used to
predict what traits offspring will have.
Sometimes one trait cannot dominate over another trait completely.
The trait will mix with the other trait. This is called
_______________ dominance. Example: _____________________
Human blood type has ______________ ______________ that can
code for the offspring. A, B, and O can make AB, A, B, AO, BO,
and OO. The O is recessive to both the A and B.
________________ ________________ occurs when a group of
gene pairs act together to produce a trait. For example,
__________________, height, and skin use multiple gene pairs.
Summary: Answer
your essential
question by
answering all of
your chunking ?s