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					           BIO 110 Introduction to Biology Take Home Genetics Test (105 points)

   1. Submit answers on the paper copy of the exam (posted as Word document on
   2. All answers must be written in your own words.
   3. You may not quote directly from the text/websites or submit a written answer
      identical to a classmate's.

Part I. Terms: (26 points)

1. Explain how the terms heterozygous and homozygous are related to homologous
chromosomes. (4 points)

2a. Although there are many types of genetic disorders, each involves changes to the cell’s DNA.
 Describe how each of the following types of genetic disorders impacts the cell’s DNA or
chromosomes. Include in your answer which of these types of disorders involves nuclear DNA
and which impacts mitochondrial DNA. (6 points)

        single gene disorder

        chromosomal disorder

        mitochondrial DNA disorder (not covered in lecture, a little research is needed – this is
not the same as a mitochondrial disorder).

2b. Give a specific example of a single-gene disorder and of a chromosomal disorder. Give a
short descriptions of each of the disorders selected.(4 points)
2c. Which of these three disorders listed in 2a can be detected by examining a karyotype?
Briefly support your answer. (2 points)

3a. Describe three ways "X"-linked traits and autosomal traits differ from each other. In
addition, describe a genetic disorder not covered in lecture that is X-linked. Reference where you
found this information. (8 points)

3b. Explain why X-linked recessive disorders are more common in males than in females. (2
Part II. Human Genetics Problems (79 points)


A. Autosomal Recessive Disorder: Cystic Fibrosis

A1. Discuss in a fair amount of detail the biological cause of cystic fibrosis. A complete answer
will include information on how the DNA is mutated, the protein that is made incorrectly in CF
patients, the consequences of this defect in the protein, and the role of the ER/Golgi. (4 points)

A2. Explain why carriers of CF, although they have an allele for the defective protein, are
healthy and symptom free. Your answer should clearly address the relationship between the
individual's DNA and the membrane proteins they make. (2 points)

A3. One of my former students has a beautiful daughter with CF, Sara Elizabeth. Both the
student and the child's father are healthy. Explain how these two healthy parents could have a
child with CF. Include in your answer the genotype of each parent and of the child. (4 points)
Please the following letter code: H - healthy h = cystic fibrosis
A4. If the couple in A3 were to have a second child, what is the risk that their second child
would have CF? Support your answer. Is the sex of the baby related to the risk of CF? Why or
why not? (4 points)

A5. With new treatments individuals affected with CF are living longer. Thus, marriage and
family are a possibility. Imagine Sara Elizabeth is grown-up and preparing to marry a healthy
man. What would you tell them/her about their risk for having children with CF? Please be sure
to consider all possibilities. For full credit, support your answer(s) with the genotypes of all
involved. (You may want to consider the best-case and worst-case scenario.) (4 points)

B. Autosomal Dominant Disorder: Marfan Syndrome

B1. Given the genetic aspect of Marafan's Flo's family was screened. (The following concerning
Flos' family is not true, but made-up for this question.) Her father and sister were diagnosed with
Marfans while her mother and a brother were given a clean bill of health. Create a pedigree
(family tree) for Flo Hyman's family -- to include: Flo, her parents, and her two siblings. Shade
in the circles/boxes of individuals with Marfan syndrome. In addition, give as much information
as possible about the genotype for each member of the family. Use the following letter key: M =
Marfan syndrome, m = healthy. (6 points)

B2. Discuss the genetic basis for Marfan Syndrome. Include in your answer information on the
gene associated with Marfan syndrome and the protein affected. Some detail is needed for full
credit. (4 points)

B3 Occasionally two healthy parents with no family history of Marfan Syndrome have a child
who is diagnosed with the condition. Explain why it would be unusual/unexpected for two
healthy parents to have a child with a dominant disorder such as Marfans. (2 points)
C. Co-Dominance - Blood Type

C1. Explain how a person could have type O blood if neither of their parents has type O blood.
Give an example of parental genotypes that support your answer. (4 points)

C2. Explain why an individual with type O blood is a universal blood donor, but can receive
blood only type O blood. Fully support your answer. (4 points)

C3. What component(s) of the plasma membrane plays a role in determining an individual's
blood type? Be specific and briefly support your answer. Base some aspect of your answer on the
information presented in Chapter 5. (FYI - The term antigen is not directly related to answering
this question.) (3 points)
C4. Although blood types can never be used to prove someone is the father of a particular child,
they can demonstrate that someone could not be the father. In 1940 there was a famous paternity
case involving Charlie Chaplin. A woman named Charlie as the father of her baby. Charlie
denied the accusation and the case went to court. At the time Charlie Chaplin was judged to be
the baby's father. At that time many states did not allow blood test results as evidence in cases of
disputed paternity. You may/must use the blood types of the individuals to guide your answer.
The baby's blood type was B, the mother's A, and Charlie Chaplin's O.

Could Charlie have been the father of this child? Support your answer by giving the genotype
(or all possible genotypes if more than one is possible) of the woman, Charlie, the baby, and the
baby's father if it's not Charlie. Be sure to include all genotypes asked for in your answer. (10


      REMINDER #2: X and Y are NOT included in the genotypes when analyzing
       disorders that are not sex-linked.

D. X-Linked Recessive: Duchenne Muscular Dystrophy
      I read a case study (true story) of a family who had a son with MD. When the son was
       first diagnosed with MD the doctor told the mother that "half on any sons she would have
       might develop MD". He also told her of the likely consequences of the disease as her son
       grew. She understood him to say that there was no medical treatment available (there is
       some that would have improved her son’s quality of life). She went on the have two
       more sons, self-diagnosed them to have MD, and did not obtain medical treatment for any
       of the sons. She has a healthy daughter. Their story came to light soon before her
       youngest son died. More detailed information on the family follows. Both the woman
       and her husband are healthy.

D1. Create a pedigree for the family in the case study. Shade in the circles/boxes of the
individuals with MD. In addition, give as much information as possible about each family
member's genotype. If more than one option is possible please show both. Don't forget this is an
X-linked disorder.

Letter Key: H = healthy h = muscular dystrophy (6 points)

D2. What did the physician mean when he/she told the woman that “half of any sons she had
might develop MD”? Was the woman correct in interpreting this as; if she had 4 boys, 2 would
be healthy and 2 would have MD? (4 points)
D3. Discuss the biological cause of Duchenne muscular dystrophy. Your answer should include
the relationship between the DNA, the proteins made, and the symptoms. (4 points)

E. X-Linked Recessive: Coloboma Iridis - NO additional research on the disorder is
needed to answer this question.

E1. (This one is not a real story. It comes from a genetics textbook) Upon the birth of their first
child the husband accuses his wife of being unfaithful. His grounds for this claim are as follows.
Both the husband and his wife have normal eyes, yet their daughter has coloboma iridis. Is the
husband's claim that he is not the baby's father grounded? Fully support your answer by giving
the genotype of the baby, mother, and the husband. In addition, give the genotype of the baby's
father if you believe it is not the husband. (6 points)

Letter Key: I = normal eyes i = coloboma iridis
E2: Fully explain how/if your answer would have been different if the baby had been a son. (4

F3: Y-Linked Trait: Hairy Ears! The allele for hairy ears is located on the Y chromosome. No
genetic information for this trait is located on the X chromosome. A man with hairy ears is
married to a woman without hair in her ears. They have 2 daughters and two sons. Would you
expect any of their children to have hairy ears? (Be as specific as possible.) Explain your answer.
(4 points)