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BI 142 – The Genetic Century
Exam 2
March 17, 2014
Name _________________________________
Advice for a good exam:
1. Read each question carefully and follow its directions.
2. Be brief! Your answer MUST fit in the space provided. A few words or a phrase may be sufficient
to answer the question. Complete sentences are not necessary.
3. Write legibly! If we can't read your answer, we cannot grade it and you will not receive credit.
1. Chromosomes are most highly condensed during mitosis. Draw a mitotic chromosome. Label the
sister chromatids, centromere(s), and the telomere(s).
What would happen to a chromosome without a
centromere?
What would happen to chromosome without a
telomere?
2. Why the Y? The Y chromosome has less than 30 active genes, compared to close to 1000 active
genes on the X chromosome. What kinds of genes are located on the Y chromosome?
What is thought to be the evolutionary relationship between the X and Y chromosomes?
How do modern X and Y chromosomes interact with each other?
3. Below each of the following karyotypes, indicate the sex of the individual represented by the
karyotype and the number of Barr bodies that would be present in the individual's cells.
Sex __________ Barr bodies _______
Sex ______________ Barr bodies _______
4. Fill in the blanks with the word(s) described in the phrases below describing cancer:
Normal cellular genes that promote growth ______________________________
Tumor that is not invasive ____________________________
Process by which tumors develop at secondary sites ____________________________
Loss of this activity increases the rate at which mutations accumulate _______________________
Both copies of these genes are inactivated when they contribute to cancers
________________________________________________
5. Cancer develops after a series of mutations occur in cellular genes. Next to each of the events listed
below, indicate whether the event would increase the frequency of cancer (), decrease the
frequency of cancer () or have no effect on the frequency of cancer ().
A mutation in one copy of an oncogene produces an inactive enzyme. _______
Both copies of the coding sequence for a DNA repair enzyme accumulate mutations that reduce
the repair activity of the enzyme. _____________
A chromosomal translocation places an oncogene under the control of a powerful promoter.
__________
A mutation in one copy of a checkpoint control gene produces an inactive enzyme. _______
A cell is exposed to ionizing radiation. ________________
6. The following statements refer to meiosis and/or mitosis. Next to each phrase, indicate whether the
phrase refers to meiosis and mitosis. Write both is it refers to both processes. Write neither if it
refers to neither process.
Increases the number of chromosomes ________________________________
Chromosomes are separated on a spindle made of proteins _________________________
Occurs in all cells of the body __________________________
Composition of individual chromosomes changes ________________________
Begins later in the lifespan of human males than females __________________________
Requires homologous pairs of chromosomes _______________________________
Used for asexual reproduction ______________________________
Timing is controlled by sex hormones ___________________________
Chromatids are connected at the centromere _____________________________
Process was first discovered in human cells ____________________________
7. An individual has the genotype AA Bb CC Dd Ee. None of the genes are located on the same
chromosome. List all the possible genotypes of the gametes that this individual would produce.
8. In green meanies, the genes for green color and meanness are on different chromosomes. Neither
trait is sex-linked. Green color is coded by a dominant allele G. Individuals who are homozygous
recessives for the green gene are yellow in color. Meanness is coded by the dominant allele M.
Individuals who are homozygous recessives for the mean gene are softies. Complete the table
below, which gives the phenotypes of parents and their offspring in 3 meanie families, by adding
the genotypes of both the mother and father parents.
Mom's
phenotype
green mean
Dad's
phenotype
green mean
green softy
yellow softy
yellow mean
green mean
Baby phenotypes
9 green mean
3 green softy
3 yellow mean
1 yellow softy
5 green softy
5 green mean
5 yellow mean
5 green mean
Mom's
Genotype
Dad's
Genotype
9. Orange and black coat colors in cats are produced from two different dominant alleles of the same
gene, which is located on the X chromosome. A female calico cat mates with an orange male. Draw
the Punnet square describing this mating and predict the phenotypes (coat colors, sex) of the kittens.
If two calico cats are produced in a litter, would you expect them to look the same? Why or why
not?
10. A genetic counselor is working with families with a history of Huntington's Disease (an autosomal
dominant disease), sickle cell anemia (an autosomal recessive disease) and hemophilia (a sex-linked
recessive disease). As she races to her office, a gust of wind blows the pedigrees describing the
inheritance of the disease genes in the three families out of her briefcase. She needs to match the
pedigrees with the family histories. In each case, she is working with the individual at the end of the
arrow. Help her out by writing the name of the disease below its pedigree. On the second line,
indicate (Yes/No) if there is a chance that her client carries the disease allele. From her work, the
counselor can identify some family members as carriers. Indicate these on the pedigree by filling in
half the symbol(s).
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