Download What are the chances?

Genetics
Name:
State Standard:
H.1L.3 -- Explain and apply laws of heredity and their relationship to the
structure and function of DNA.
Score
10
Response
Excellent
8
Proficient
6
Adequate
4
Incorrect
1
Fails to complete
Scoring Rubric 1-4
Responses are clear, complete and demonstrate a thorough
understanding of the subject matter
Completes the assignment or experiment satisfactorily, but
the explanations have minor flaws
Begins the assignment and explanation satisfactorily; but
omits significant parts or fails to complete.
Assignment and its explanations are not accurate. Group did
not demonstrate understanding or authentic knowledge
Fails to complete
WHAT ARE THE CHANCES?
Background: Genetic disorders are abnormal conditions that are inherited through genes or
chromosomes. Some genetic disorders are caused by mutations in the DNA of genes. Others are
caused by changes in the overall structure or number of chromosomes.
Cystic fibrosis is a genetic disorder in which the body produces unusually thick mucus in the
lungs and intestines. This makes it difficult for a person with cystic fibrosis to breathe or digest food.
Cystic fibrosis is caused by a recessive allele (f). At this time, the symptoms of cystic fibrosis can be
controlled, but there is no cure for this disease.
In this lab, you will determine the probability that cystic fibrosis will appear in the children of a
couple who carry the traits for disease.
Procedure:
1. Read the following family history: Anthony and Emma have a daughter named Kathryn. Kathryn
has been diagnosed with cystic fibrosis. Anthony and Emma are both healthy. Anthony’s parents are
both healthy. Emma’s parents are both healthy. Anthony has a brother, named Corbin, who has cystic
fibrosis.
2. In the space in the Data and observations section, draw a pedigree that shows all the family
members mentioned here. Use circle to represent the females and squares to represent the males. Shade
the circles or squares representing the people who currently have cystic fibrosis.
3. Determine Kathryn’s alleles. Write her genotype next to the pedigree symbol for Kathryn.
Remember: Cystic fibrosis is a recessive condition.
4. Determine Corbin’s alleles and write the genotype next to his symbol.
5. Determine what genotypes Anthony and Emma must have. Write their genotypes next to their
pedigree symbol.
6. Determine all the POSSIBLE genotypes of the other family members. Fill in each person’s
genotype next to their symbol in the pedigree. Write in all possible genotypes.
Data and Observations
1. Use this space to draw a pedigree of Anthony and Emma’s family.
(P)
(F1)
(F2)
Analyze and Conclude
1. What were the genotypes of Anthony’s parents?
2. What were the genotypes of Emma’s parents (3 possibilities)?
3. Anthony also has a sister, Zoe. What is the probability that
she has cystic fibrosis? Use the punnet square to explain.
4. What is the probability that Anthony and Emma
will have another child with cystic fibrosis?
5. Why is information about several generations of family members necessary to get a good idea
about a hereditary condition? Explain.
6. Do you think cystic fibrosis is a sex-linked genetic disorder? Explain.