Gummy Bear Genetics

<strong>Genetics</strong> STAO 2010<br />

<strong>Gummy</strong> <strong>Bear</strong> <strong>Genetics</strong><br />

Purpose<br />

To determine the genotypes of parents by counting and sorting the phenotype ratios of their offspring.<br />

Procedure:<br />

1. Empty the contents of the bag onto your desk. Count the gummy bears and record the total in Table<br />

2. Sort the gummy bears into groups based on phenotype differences that can be easily observed and<br />

quantified, such as colour.<br />

3. Count and record the number of bears of each phenotype in the table below.<br />

4. Repeat Steps 2 to 5 for each of the different bags.<br />

Monohybrid<br />

Cross sample<br />

Total number<br />

of gummy<br />

bears<br />

Phenotypes<br />

and numbers<br />

Phenotype<br />

Ratio<br />

Genotypes<br />

Parental Cross<br />

A<br />

B<br />

C<br />

Analyze and evaluate:<br />

a) For each bag, calculate the phenotype ratio of bears in the bag. Record this ratio in the table.<br />

b) Determine which bear colour is dominant and which bear colour is recessive. Use T to represent the<br />

dominant allele and t to represent the recessive allele. Hint: look at the phenotype ratio of Bag C.<br />

c) Use the ratios and your knowledge of Mendelian genetics to determine the likely genotype(s) of<br />

each type of bear found in the bags. Record these genotypes in the table.<br />

d) Determine the genotypes of the parents that produced the off spring in each of the bags. Record<br />

this information in the table.<br />

e) For each bag, draw a Punnett square to show that the cross of the genotypes you predict for the<br />

parents that would produce the ratio that you observed.<br />

Cross A Cross B Cross C<br />

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My Genetic Profile Worksheet<br />

Human genetic characteristics and phenotypes<br />

Characteristic Dominant Phenotype Recessive Phenotype<br />

Dimples Present (D) Absent (d)<br />

Hairline Widow’s peak (W) Straight (w)<br />

Tongue rolling Roller (R) Non‐roller (r)<br />

Thumb placement with folded<br />

hands<br />

Left thumb on top (P)<br />

Right thumb on top (p)<br />

Parent #1 Parent #2<br />

Phenotype Genotype Phenotype Genotype<br />

Dimpled Dd Dimpled Dd<br />

Straight<br />

Widow’s peak<br />

ww<br />

hairline<br />

Ww<br />

Tongue roller Rr Non‐ roller rr<br />

Right thumb<br />

on top<br />

pp<br />

Child (F1)<br />

Phenotype Genotype<br />

Right thumb<br />

on top<br />

pp<br />

Grandchild (F2)<br />

Phenotype Genotype<br />

Pedigree Chart for a SINGLE characteristic<br />

Parent #1<br />

____<br />

Parent #2<br />

_____<br />

Parent #3<br />

_____<br />

Parent #4<br />

_____<br />

Child #1<br />

_____<br />

Child #2<br />

_____<br />

Grandchild<br />

_____<br />

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What are the chances?<br />

In this investigation you will model a cross between two heterozygous individuals. You will then<br />

determine the genotype and phenotype ratios of your model F1 generation. In addition, you will<br />

investigate the role that sample size and probability play in producing a 25:50:25 ratio in the F1<br />

generation.<br />

Equipment and Materials: two small opaque bags containing 40 beads each (20 blue beads and 20 red<br />

beads)<br />

Note: Red beads are the dominant allele, R, for red flowered, and the blue beads are the recessive allele,<br />

r, for blue flowered. Together, the two pouches represent the parent generation.<br />

Without looking, draw one bead from bag 1 (P1) and one bead from bag 2 (P2).<br />

This represents the joining of two gametes to form a new individual. Record the “genotype” of this<br />

offspring. Return the “gametes” to their original bags. Repeat for a total of 20 times.<br />

Offspring Genotypes<br />

1 2 3 4 5 6 7 8 9 10<br />

11 12 13 14 15 16 17 18 19 20<br />

Expected Genotype ratio:<br />

Expected Phenotype ratio:<br />

______ RR : ______ Rr: ______ rr<br />

______ Red : ______ Blue<br />

Actual Genotype ratio:<br />

Actual Phenotype ratio:<br />

______ RR : ______ Rr: ______ rr<br />

______ Red : ______ Blue<br />

How did your results compare to the expected ratio?<br />

How did the total class results compare to the expected ratio?<br />

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Explore an Issue in Genetic Screening: Who Wants to Know? Who<br />

Needs to Know?<br />

The Issue<br />

The ethics of legal access to, and ownership of genetic information needs to be considered carefully as<br />

technology for collecting and testing genetic disorders and other inherited characteristics increases.<br />

Who decides? Who wants to know? Who should know? Who should we be required by law to tell?<br />

Brainstorm a list of FIVE people that might have an interest in knowing YOUR DNA – then list the<br />

possible benefits and risks of their knowing – to them and to you!<br />

Who? Benefits Risks<br />

You may wish to consider the following situations:<br />

• Parenting: Should parents be able to test their children for any genetic disorder or trait?<br />

• Relationships: Should people have access to a potential partner’s genetic information? What if your<br />

partner might develop Huntington’s disease? Should you have the legal right to know?<br />

• Employment: Should prospective employers have access to genetic information about an applicant?<br />

If so, how much of this information should be used to determine eligibility for employment? For<br />

example, should an airline be able to screen its pilots for a gene that increases the risk of a heart<br />

attack?<br />

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