Name: ____________________________________________   Period: _________

Lab: Gummy Bear Genetics

 

Background:

Gummy bears are classified as endangered species, primarily because of predation by many members of the species Homo sapiens, which devour the gummy bears like candy.  A captive breeding program has been instituted to keep the gummy bears safe from consumption and studying this fascinating species.

As a result of these studies, scientists have recently discovered that skin color in gummy bears is controlled by a single gene that has multiple alleles.  Four alleles for this gene exist in the species, a green allele, a white allele, a red allele and a yellow allele.   There are three modes of inheritance that are associated with these multiple alleles for gummy bear skin color: Mendelian dominance, incomplete dominance, and codominance.  The relationship between the alleles is shown in the table below.

 

Mode of inheritance

Gummy Bear Genotypes and Phenotypes

Mendelian Dominance

Green (G) is dominant to white (g)

 

Incomplete Dominance

Red (R) is incompletely dominant to Yellow (R’) producing orange offspring (RR’)

Codomiance

Green (G) is codominant to Red (R) producing a christmas bear (RG) part red and part green.

 

Materials: 1 bag of gummy bear parents and 6 sets of offspring.

 

Purpose: To determine patterns of inheritance in gummy bear coat color and parent genotypes from the offspring phenotypic ratios.

 

Procedure:

  1. Obtain 6 sets of gummy bear offspring and one parent pool bag.
  2. Look at offspring set 1. Do not remove the offspring from the bag! Write the phenotypic ratio of the offspring in the space provided under the offspring #1. 
  3. Use the Punnett square under “Offspring 1” to work backwards and determine the genotypes of the parents.  Show all work.
  4. Write the genotypes of the parents in the space provided under offspring #1.
  5. Remove the appropriate gummy bear parent from the bag and place them on top of the offspring bag. 
  6. Record the phenotypes of the parents in the space provided under offspring #1.
  7. Record the mode of inheritance in the space provided under offspring #1. 
  8. Repeat numbers 3-8 of the procedure for the other sets of offspring.

 

 

 

 

 

 

 

 

 

 

 

Data:

Offspring Bag #1

Phenotypic Ratio: ______________________ (remember to include zeros!)

 

 

 

 

 

 

 

 

Parent Genotypes: __________  X  _________      

 

Parent Phenotypes: ___________________  X ____________________

 

Mode of inheritance: _________________________________________

 

Offspring Bag #2

Phenotypic Ratio: ______________________ (remember to include zeros!)

 

 

 

 

 

 

 

 

Parent Genotypes: __________  X  _________      

 

Parent Phenotypes: ___________________  X ____________________

 

Mode of inheritance: _________________________________________

 

Offspring Bag #3

Phenotypic Ratio: ______________________ (remember to include zeros!)

 

 

 

 

 

 

 

 

Parent Genotypes: __________  X  _________      

 

Parent Phenotypes: ___________________  X ____________________

 

Mode of inheritance: _________________________________________

 

Offspring Bag #4

Phenotypic Ratio: ______________________ (remember to include zeros!)

 

 

 

 

 

 

 

 

 

Offspring Bag #4

 

Parent Genotypes: __________  X  _________      

 

Parent Phenotypes: ___________________  X ____________________

 

Mode of inheritance: _________________________________________

 

Offspring Bag #5

Phenotypic Ratio: ______________________ (remember to include zeros!)

 

 

 

 

 

 

 

 

Parent Genotypes: __________  X  _________      

 

Parent Phenotypes: ___________________  X ____________________

 

Mode of inheritance: _________________________________________

Offspring Bag #6

Phenotypic Ratio: ______________________ (remember to include zeros!)

 

 

 

 

 

 

 

 

Parent Genotypes: __________  X  _________      

 

Parent Phenotypes: ___________________  X ____________________

 

Mode of inheritance: _________________________________________

 

Analysis:

  1. Gummy bear skin color is controlled by multiple alleles. Describe what this means?

 

 

 

  1. How many alleles control gummy bear skin color? Write the letter symbol that represents each allele.

 

 

 

  1. Explain how a heterozygous individual's phenotype for incomplete dominance differs from a heterozygous individual's phenotype for codominance.