Download punnet-square-bears - Coastal Carolina University

Gummy Bear Genetics
Kim Trinkle, Coastal Carolina University GK-12 Fellow
Adapted from Alison M. Cawood (www.Earthref.org)
SC Science Standard 7-2.5: Summarize how genetic information is passed from
parent to offspring by using terms such as genes, chromosomes, inherited traits,
genotype, phenotype, dominant traits, and recessive traits
SC Science Standard 7-2.6: Use Punnett squares to predict inherited monohybrid
traits.
Materials:
Brown paper bags (enough for 2 per each group)
Gummy bears separated into green and yellow (enough for at least 8 per group)
Before lab: Fill one of the brown paper bags with a random assortment of yellow and
green Gummy Bears.
Introduction: The rare and elusive wild gummy bear is unfortunately endangered
due to its extreme tastiness! However, you can help. The Columbia Zoo has
received a pair of wild gummy bears to breed in captivity so that offspring might be
released into the wild. The zoo directors have heard about your recent studies in
genetics and have selected you to help them with their project.
Gummy Bear Characteristics
Gummy Bears come in two different colors: Yellow and Green
The Genotype for a Yellow gummy bear can either be: BB or Bb
The Genotype for a Green gummy bear can only be: bb
Questions for Review
1. In the scenario above, Yellow coloration is the dominant/recessive (circle one)
trait.
2. If I tell you a gummy bear is yellow, I am describing its phenotype/genotype
(circle one)
3. If I tell you a gummy bear has two recessive alleles, I am describing its
phenotype/genotype (circle one). What color (yellow or green) would this bear
be?
Step 1: Selecting the Parent Generation
Without looking, randomly choose two gummy bears to be the “parents” of the future
gummy bear generations. Write down the phenotypes and genotypes of each
parent in the space below. If you pick a yellow gummy bear, you will have to pick
which genotype you want to use.
Parent 1: Phenotype: ________________
Parent 1: Genotype: _________________
Parent 2: Phenotype: ________________
Parent 2: Genotype: _________________
Step 2: Predicting the Offspring (generation 1)
Fill in the Punnett Square below to predict the traits of the future offspring of these
two bears.
Write the possible colors of each offspring and the percent of offspring of each color
that you would expect.
Fill another bag with 4 gummy bears representing the number of each color you
would expect to see from the cross above.
Randomly pick one gummy bear from the bag…this will serve as offspring #1
1. What color is offspring #1? ____________________
Put the gummy bear back into the bag so that there are 4 gummy bears in the
bag
Randomly Draw a gummy bear from the bag…this will serve as offspring #2
2. What color is offspring #2?___________________
Repeat the steps above until you have data for four offspring total. Make sure you
put the gummy bear back into the bag every time you take it out!!!
3. What color is offspring #3?__________________
4. What color is offspring #4? __________________
5. Did the Punnett square accurately predict the percentages of each color for what
you actually found? If not, why do you think this is?
If so, do you think that Punnett Squares always accurately predict the outcomes
of the cross of two organisms? Why or why not?
Producing a different generation using new information
Ms. Trinkle and her fellow scientists at Coastal Carolina University have closely been
monitoring what is left of the remaining gummy bear population in the wild. This
research team has found that green gummy bears in the wild survive better than yellow
ones because they can camouflage themselves against the trees.
Using this information, what color parents would you tell the biologists at the zoo to
cross to produce offspring that are better to camouflage themselves in the wild?
Parent 1 phenotype should be: _______________
Parent 1 genotype should be: ________________
Parent 2 phenotype should be: _______________
Parent 2 genotype should be: ________________
Fill in the Punnett Square below using these two parents
According to this cross, __________% of the offspring produced from these parents
should be green.
Why did both parents have to be green?
Do you think selectively breeding so that you get only one genotype in the offspring (in
other words what the biologists at the zoo above did) is a good idea? Why or why not?
Maintaining genetic diversity
Scientists at the Columbia Zoo still want to keep genetic diversity in the released
populations of gummy bears, so they decide to also breed Yellow gummy bears for
release. Additionally, Ms. Trinkle and her group of scientists have just published an
article in the major scientific journal, Science, about a new mutation that has been
occurring in green gummy bears.
This mutation only affects the allele, b, but not the allele, B.
A gummy bear with genotype BB is not affected.
A gummy bear with genotype Bb is still affected by the mutation, but can live as normal
they are known as carriers
A gummy bear with genotype bb is doubly affected and cannot live at all.
Scientists want to produce a generation that has a high amount of survivors but is still
genetically diverse. What parent genotypes should they use?
Fill in the Punnett square below with your final answer
Why can bears with the genotype Bb still live normally even though they have the
affected gene?