Name_________________________________________
December 14, 2004
BIO184 Genetics
Exam 3
This examination is worth 100 points. There are 24 questions on 6 pages. Read through
the questions completely before answering the questions. If you are unclear about a
question, please ask me.
Good luck
Part A: Multiple Choice: Answer with the best choice. Make sure that you clearly circle the
correct answer and erase any erroneous marks. (4 pts each)
1. A mutation that changes a codon sequence, and subsequently changes the amino acid
that should have been placed at that point in the polypeptide chain, is called a:
a. frameshift mutation
b. missense mutation
c. silent mutation
d. nonsense mutation
2. Transcription occurs in the _________ and translation occurs in the _________ of
PROKARYOTIC cells.
a. nucleus; cytoplasm
b. cytoplasm, nucleus
c. nucleus; nucleus
d. cytoplasm, cytoplasm
3. Protein synthesis begins with the amino acid ___________, as its codon is the one used
as the “start codon” by nearly all organisms.
a. methionine
b. arginine
c. cysteine
d. leucine
4. Anabolic pathways involved in the synthesis of essential molecules (e.g. trp operon) are
usually regulated by:
a. end products of the pathway
b. substrate of an enzyme in the pathway
c. other metabolites that are limiting
d. none of the above
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5. In the genotype presented below, what will the expression phenotype for permease be
(I+p+ocZ-Y- / I+p+o+Z-Y+)
a. constitutive
b. inducible
c. absent
d. lethal
6. What term describes a second level of regulation of the trp operon that occurs in TrpR¯
mutants suggesting that it is repressor independent?
a. truncation
b. derepression
c. attenuation
d. antisense RNA
7. Transcription in prokaryotes and eukaryotes is similar in that:
a. transcriptional machinery controls compaction and decompaction of chromatin
b. the mRNA produced can undergo alternative splicing
c. both prokaryotic and eukaryotic proteins have identical affinities for DNA
d. both are contained within the cell nucleus
e. both are regulated by attachment of proteins to DNA adjacent to the gene
being transcribed
8. The primary structure of a protein is directly associated with ______.
a. regular repeating shapes, such as beta-sheets
b. the three-dimensional shape of the protein
c. the linear sequence of the amino acids
d. the interaction of two or more peptide chains
9. In prokaryotic systems, which of the following typically stops the process of translation?
a. rho proteins
b. aminoacyl tRNA synthase
c. rRNA
d. stop codons
e. introns
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10. Following transcription, the RNA has a complementary sequence of which of the
following?
a. regulatory sequences
b. termination sequences
c. the coding strand of DNA
d. the template strand of DNA
e. none of the answers are correct
11. Which of the following provides for a higher level of stability in the mRNA?
a. alternative splicing
b. RNA editing
c. 5' capping
d. 3' polyA tailing
e. trimming
12. What do both the rho-dependent and rho-independent mechanisms of termination have
in common?
a. Terminate transcription immediately after the stop codon.
b. A sequence rich with A-U base pairs.
c. Both require a helicase to separate the DNA-RNA complex.
d. Formation of a stem-loop structure.
13. Which of the following is not an example of translational regulation in prokaryotes?
a. sterically blocking the ribosome
b. phosphorylation of an enzyme
c. incorporation of antisense RNA
d. altering the structure of the mRNA
14. In the following sequence of DNA, the bold italicized base has been mutated. What type
of base substitution is this?
5' - G A T C T C C G A A T T – 3'
original strand
5' - G A T C T C C C A A T T – 3'
mutated strand
a. transition
b. transversion
c. neither
15. (True or False) Darwin's theory of natural selection supported the directed mutation
theory.
_F, spontaneous mutation____________
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16. The complete loss of either a guanine or adenine from DNA is an example of _____.
a. depurination
b. tautomeric shifts
c. deamination
d. none of the answers are correct
17. For a quantitative trait, the total variance of the population is due to which of the
following?
a. the amount of variance due to genetic factors only
b. the amount of variance due to environmental factors only
c. the difference between the variance attributed to genetic and environmental
factors
d. the sum of the genetic and environmental variances
18. Heritability may be calculated as which of the following?
a. the total variance minus environmental variance
b. total variance minus genetic variance
c. genetic variance divided by environmental variance
d. genetic variance divided by total variance
e. none of the answers are correct
19. Microevolution is defined as:
a. a process that includes new species formation
b. changes in the frequency of alleles within a population
c. evolution of microorganisms
d. interactions between species
e. all of the above
20. Which of the following terms represents homologous genes that are found in different
species?(meaning the same gene but found in different species)
a. paralogs
b. orthologs
c. gene families
d. none of the answers are correct
PART B - Fill in the blank and short answer. Please write clearly.
21. Splicing of eukaryotic RNA molecules removes the __introns_______ and links together
the ___exons__________ within the genetic sequence (4 pts).
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Short answer:
22. The genetic code is described as being nearly universal, degenerate, and
nonoverlapping. Briefly describe what each of these properties refers to (6 pts).
23. In the example of the lac operon, and most operons, what is the significance of a
polycistronic message? (First define polycistronic message)(4 pts)
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24. In the presence of glucose, lactose, or glucose + lactose, what would be the effect of
the following loss of function mutations: allolactose-binding domain of lac repressor,
CAP site, and adenylyl cyclase?(6 pts)
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