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November 8, 2006
BIO 184 Genetics
Exam 2
This examination is worth 100 points. There are 33 questions on 7 pages. Read through
the questions completely before answering. If you are unclear about a question, please ask
me.
Part A: Multiple Choice: Answer with the best choice. Make sure that you clearly circle the
correct answer and erase any erroneous marks. (2.5 pts each)
1. The degeneracy of the genetic code refers to the following occurrence:
a. same number of codons as there are amino acids
b.
c.
d.
e
more amino acids than codons
the code is used by nearly every living organism
some amino acids have multiple codons
only one nucleotide triplet codes for an amino acid
2. The pattern or sequence in which a molecule of mRNA is deciphered by a ribosome is
called the:
a. code degeneration
b. peptide transition
c. reading frame
d. P site
e. A site
3. Which of the following is not true about the ribosome binding site (rbs):
a. inhibitory proteins can bind to the rbs and prevent translation
b. the rbs is a consensus sequence
c. the rbs is found on the 5’ untranslated region (UTR)
d. the rbs binds to a complementary region within the small ribosomal subunit
e. none of the above
4. Which of the following is not a property of an anticodon?
a. corresponds to the amino acid it carries
b. complementary to the codon
c. modified bases are often found within it
d. the wobble position is at the 3’ end of the anticodon triplet
e. none of the above
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5. The enzyme that attaches free amino acids to the tRNA molecule is called:
a. peptidyl transferase
b. aminoacyl tRNA synthetase
c. ligase
d. polymerase
e. amino acid attachase
6. 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
e. none of the above
7. Transcription occurs in the _________ and translation occurs in the _________ of
EUKARYOTIC cells.
a. nucleus; cytoplasm
b. cytoplasm, nucleus
c. nucleus; nucleus
d. cytoplasm, cytoplasm
8. In prokaryotic systems, which of the following typically stops the process of
translation?
a. rho proteins
b. aminoacyl tRNA synthetase
c. rRNA
d. stop codons
e. introns
9. In the following sequence of DNA, the italicized, bold base has been mutated. What type
of mutation 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 A A A T T – 3'
mutated strand
a.
b.
c.
d.
e.
frameshift
missense
transition
transversion
neutral
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10. Catabolic pathways (e.g. lac operon) that break down complex substances into more
usable units are usually regulated by the:
a. end products of the pathway
b. substrate (or related compound) of an enzyme in the pathway
c. other metabolites that are limiting
d. attenuation
e. none of the above
11. In the genotype presented (genomic plus plasmid genes), what will the expression
phenotype for beta galactosidase be (I+ P+ Oc Z+ Y- // I- P+ O+ Z- Y+)
a. constitutive
b.
c.
d.
e.
inductive
completey absent
basal expression only
lethal
12. How does Tryptophan function in attenuation of the trp operon?
a. tryptophan binds to the repressor preventing it from binding to DNA thus allowing
transcription of the operon
b. tryptophan binds to the stem-loop structures and prevents transcription
c. an abundance of tRNAs charged with tryptophan cause ribosome stalling
d. the lack of tRNAs charged with tryptophan allows stem-loop structures to form that
allows transcription
e. RNA polymerase directly senses the amount of tRNAs charged with tryptophan
13. What site on the ribosome is primarily responsible for holding the growing polypeptide?
a. A
b. E
c. P
14. Antisense RNA does which of the following?
a. inhibits the formation of the open complex in transcription
b. occupies the A and P sites of the ribosome
c. binds to the mRNA and prevents translation
d. prevents the correct folding of a newly formed peptide
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15. Eukaryotic DNA methylation is involved in all the following except:
a. regulating transcription by methylation at CpG islands
b. enhancing heterochromatin formation
c. protect “self” (meaning their genome) from restriction enzymes
d. methylation-directed mismatch repair
e. none of the above
16. Which one of the following is not a mechanism that regulates eukaryotic transcription
factor activity?
a. protein dimerization
b. hormone binding
c. phosphorylation
d. attenuation
e. none of the above
17. The regulation of protein function (e.g. feedback inhibition of enzymes), not gene
expression, is called ________ regulation.
a. post-translational
b. transcriptional
c. translational
d. post-transcriptional
18. An organism with four sets of chromosomes, two from one species genome and two
from a different species genome is called:
a. aneuploid
b. autotetraploid
c. allotetraploid
d. autopolyploid
e. tetrasomy
19. Which of the following types of plants would usually be a seedless variety?
a. aneuploid
b. diploid
c. triploid
d. tetraploid
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20. When two sister chromatids end up in the same gamete, non-disjunction has occurred in:
(hint: remember the colorblind example we covered in lecture)
a. first division of meiosis
b. second division of meiosis
c. either division of meiosis is consistent
d. both divisions of meiosis
21. Homologous chromosomes must separate from one another and move to opposite poles
during:
a. mitosis
b. meiosis I
c. meiosis II
d. both a and b
e. both a and c
Part B: Fill in the blank (2.5 pts each)
22. Thymine dimers are caused by _______________________.
23. DNA that contains instructions for including two or more structural genes on a single
transcript is termed a ____________________________ mRNA.
24. A mutation in a gene that restores the wild type phenotype of a second gene is called a
__________________________ mutation.
Part C. Next to each of the following, determine whether they are cis-acting elements or
trans-acting factors. Place the term cis or trans in the blank. (2 pts each)
25. Operator
___________
26. TrpR
___________
27. Enhancer
___________
28. lacZ
___________
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Part D- Short answers (please write clearly and use the back of the page if needed):
29. Explain what a frameshift mutation is and what possible effects it has on a protein
sequence. (4 pts)
30. A cross between a male donkey (62 chromosomes) and a female horse (64
chromosomes) produces a mule (63 chromosomes). Why are allodiploid species such
as the mule usually infertile? (4 pts)
31. Why would a triploid individual be infertile? (4pts)
32. E. coli exhibit a diauxic growth shift caused by their regulation of sugar metabolism
when glucose and lactose are in their medium.
a. Explain what is meant by the term diauxic growth and illustrate the growth curve
(4 pts).
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b. Explain how the levels of glucose during this diauxic growth shift contribute to the
regulatory mechanism. Be sure to include CAP in your explanation. (8 pts)
33. You have been given a purified chemical compound named “humic”, a derivative of lignin
that is a byproduct from timber mills. You have been asked to test whether humic has
mutagenic properties. How would you go about testing this compound? Be sure to use
a negative control in your experimental design. (hints: Ames test, salmonella, his-) (8
pts)
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ANSWERS:
1.
d
2.
c
3.
e
4.
d
5.
b
6.
a
7.
a
8.
d
9.
c
10.
b
11.
a
12.
d
13.
e
14.
c
15.
c
16.
d
17.
a
18.
c
19.
c
20.
b
21.
b
22.
uv light
23.
polycistronic
24.
intergenic suppressor
25.
cis
26.
trans
27.
cis
28.
trans
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