GENETICS - BIOL 7 EXAM III -
November 10, 2005 NAME:
DO NOT USE ANY OTHER PAPER AT ANY TIME WITHOUT INSTRUCTOR PERMISSION
Part I: [51 points] Choose the one BEST answer. Circle its
letter. Read each question and all 5 choices carefully because more
than one answer might seem correct at first glance. 1.5
points each
1. In the E. coli lac operon system, the lac repressor
binds to the
a. operator
b. promoter
c.
structural genes
d.
transcribed mRNA
e. CAP
2. Gyrase
a. nicks
the DNA helix to relieve supercoiling
b. is not
a topoisomerase
c. adds to
the effects of helicase
d. causes
positive but never negative supercoiling
e. cannot
repair its own nicks
3. The triplet of nucleotides in tRNA that is complementary to a
triplet of nucleotides in mRNA is called a(n)
a. codon
b.
anticodon
c.
antiparallel triple
d.
repressor
e. none of
the above
4. The type of genetic exchange in which avirulent Streptococcus
pneumoniae become virulent by being exposed to heat-killed virulent
cells was (and still is) called
a.
conjugation
b.
transformation
c.
transduction
d.
incomplete dominance
e.
co-dominance
5. In a particular species, genotypes CCPP, CCPp. CcPP, CcPp form
wild type purple flowers, while Ccpp, Ccpp, ccPP, and ccPp form mutant
white flowers. Thus, one can infer that
a. the C
allele results in the wild type, purple flowers
b.
homozygous dominant alleles at either C or P masks the wild type
c.
homozygous recessive alleles at either C or P masks the wild type
d. the P
allele results in the wild type
e. C and P
are codominant
6. A dihybrid test cross was undertaken to study two genes that
assort independently; offspring were observed in a 12:3:1 phenotypic
ratio. The best explanation is that
a. four
phenotypes will result from this cross, so these data are incorrect
b. four
phenotypes will result from this cross, so the cross was not a test
cross
c. I
obviously was mistaken about the fact that the genes are on two
different chromosomes
d. a
and/or b
e. all of
the above
f.
epistasis is the simplest explanation of these data
7. Transcription
a. always
occurs on both strands of DNA in the same region
b.
involves large portions of the DNA at a time
c.
involves small portions of the DNA at a time
d. a and b
e. a and c
8. Sex-limited phenotypes are due to
a. sex
linked genes
b.
autosomal genes
c. the
answer depends on which sex the phenotype is limited to
d.
epistasis
e.
environment
9. Which of the following are involved in disrupting the DNA
double helix to permit replication?
a. helicase
b. gyrase
c. single
stranded DNA binding protein
d.
topoisomerase
e. all of
the above
10. Deviation from the expected 9:3:3:1 ratio in the F2 can imply
a. gene
interaction
b. gene
linkage
c.
recombination
d. a and b
e. all of
the above
11. hhIAIB will have the same phenotype as
a. Hhii
b. hhIAIA
c. Hhii
d. hhii
e. all of
the above
12. The term replicon refers to
a. DNA
that replicates under the control of one origin of replication
b.
unidirectional replication from a single fork
c.
replication of the entire E. coli genome
d.
replication of an entire plasmid
e.
replication of an operon
13. The tRNA which will read the mRNA 5’- CGU -3’ will have the
anticodon
a. 5’-
ACG-3’
b. 5’-
GCG-3’
c. 5’-
GCA-3’
d. 5’-
GCG-3’
e. a or b
f. c or d
14. A substance which, when injected in an organism, causes that
organism to make antibodies is a(n)
a.
antibiotic
b. antigen
c. vaccine
d. SDS
e.
streptomycin
15. The precursor of cAMP is
a.
adenylate cyclase
b. cADP
c. cATP
d.
allo-lactose
e. ATP
16. In bacteria, set of genes under the control of a single DNA
promoter and its control elements is a(n)
a.
regulator
b. operator
c.
activator
d. operon
e. inducers
17. Ribosomes are made of all of the following EXCEPT
a.
ribonucleoprotein
b. DNA
c. RNA
d.
ribosomal RNA
e. protein
18. Primase activity results in the formation of an RNA/DNA
heteroduplex, which is ultimately replaced with dsDNA by
a. DNA pol
I converting RNA to DNA moieties
b. DNA pol
I degrading RNA and replacing it with DNA
c. DNA pol
III converting RNA to DNA moieties
d. DNA pol
III degrading RNA and replacing it with DNA
e. DNA pol
I degrading RNA and DNA pol III synthesizing new DNA in its place
19. The lagging strand of the replication fork moves in the
direction of
a. 5'
–> 3'
b. 3'
–> 5'
c. the
lagging strand does not move, but it is synthesized 5' –> 3'
d. the
lagging strand does not move, but it is synthesized 3' –> 5'
e. the
lagging strand does not move; it is synthesized in a 5' –> 3'
direction overall, but in 3' –> 5'fragments
f.
the lagging strand does not move; it is synthesized in a 3' –> 5'
direction overall, but in 5' –> 3'fragments
20. DNA pol I
a.
catalyzes chain synthesis 5' to 3'
b. removes
mismatched bases using 3'-5' exonuclease activity
b. removes
mismatched bases using 5'-3' exonuclease activity
d. a and b
e. all of
the above
21.- 24. DNA polymerase III requires each of the following; match
the substance with its purpose:
a free 3' -OH end upon which to build
nascent DNA
the energy to catalyze the synthesis of nascent DNA
a DNA template which can be copied a 3'-5' exonuclease proofreading
activity
a. ATP
b. dNTP
c. primer
d. pre-existing dsDNA
e. DNA pol III
25. tRNA molecules are charged by
a.
peptidyl transferase
b.
aminoacyl-tRNA synthetase
c.
translocase
d.
aminoacyl-tRNA connectase
e.
ribosomes
26. The presence of lactose causes the lac operon to be
transcribed because lactose
a. binds
to the CAP site on the promoter region, enhancing RNA polymerase binding
b. cannot
be transported into the cell
c. binds
to the allosteric site of the repressor, inhibiting DNA binding by the
repressor
d. binds
to the RNA polymerase, enhancing its ability to bind the promoter
e. binds
to the allosteric site on the lactose permease, increasing lactose
entry into the cell
27. Buoyant density centrifugation usually employs
a. SDS
(sodium dodecyl sulfate)
b. CsCl
(cesium chloride)
c. sucrose
d. any of
the above will do
e. none of
the above will work
28. DNA ligase
a. joins
pieces of ssRNA by catalyzing by formation of phosphodiester bond
b. joins
pieces of ssDNA by catalyzing by formation of phosphodiester bond
c. is the
only enzyme can seal the DNA chain
d. b and c
e. all of
the above
29. DNA polymerase I can do all of the following EXCEPT
a. start
chain growth in 5' –> 3' direction
b.
synthesize DNA 5' –> 3'
c. repair
damaged DNA
d. remove
mismatched bases with its 3' –> 5' exonuclease activity
e. remove
mismatched bases with its 5' –> 3' exonuclease activity
30. DNA differs from RNA in that
a. DNA
contains 2'-deoxyribose while RNA contains ribose
b. RNA is
usually single stranded while DNA is usually double-stranded
c. DNA is
much more stable under all circumstances than is RNA
d. a and b
e. all of
the above
31. Hershey & Chase incorporated a radioisotope
of
into the DNA
and
into the protein of separated phage cultures
a. S .... P
b. P .... S
c. C .... S
d. P .... C
e. they
did not use radioisotopes at all
32. A blood type O individual, whose parents’ blood types are B
and AB, is genetically type B. She is
a.
homozygoous recessive for H substance
b. ii
c. an
example of co-dominance
d. either
a or b can explain this individual's phenotype
e. none of
the above: this case can never exist in real life
33. Familial prostate cancer is certainly
a.
sex-linked
b.
sex-influenced
c.
sex-limited
d.
sex-linked and sex-limited
e.
sex-influenced and sex-linked
34. Nothing changes as much as Schmeidler’s office hours seem to
this semester. They are now M 7:30-9:30 am, T-Th 7:30-8am &
1:20-1:50 pm, T 4-5 pm.
a. I
already knew that because I looked on the web site
b. OK, I
know that now
c. no, it
isn’t
d. I don’t
understand - when are the office hours?
e. all of
the above
Part II: [50 points] Answer each question completely and
clearly. Show your work for possible partial credit. Make
sure your answer is clearly stated, and easy to find. Make sure
you have answered all the parts of the question.
1. [15 pts] The following DNA sequence is a fragment of a much
longer piece. Based on the presence of an open reading frame for
translation, answer the following. For each mutation, use
correct terminology to describe the mutation and its effect.
↓
5' .... G-T-T-G-A-A-G-G-G-C-A-C-G-T-C-A-G-A-T-A-A-C-A-T-A-G-T-A-G-C-
.... 3'strand 1
3' .... C-A-A-C-T-T-C-C-C-G-T-G-C-A-G-T-C-T-A-T-T-G-T-A-T-C-A-T-C-G-
.... 5'strand 2
a. If this DNA codes for a polypeptide, which is the template
strand? (strand 1 or 2?)
b. Write the mRNA sequence that would be transcribed.
c. Write the polypeptide that would be translated.
d. If the G-C indicated above were mutated to a A-T, what
polypeptide would be translated?
e. If, INSTEAD, a T-A were inserted just to the left of the same
G-C, what polypeptide would be translated?
2. [12 pts]
a. Draw a molecule of RNA with the sequence ACUG. It is not
necessary to include the details of the nitrogenous bases, as long as
their basic structure/shape is indicated.
b. Draw the DNA which
would encode this RNA.
c. Draw one precursor molecule for RNA and one for DNA (any base)
3. [8 pts] What is a consensus sequence? Define or explain
what the term means, and its significance or how it is important in the
systems we have been discussing. Give 2 examples of consensus
sequences: not the actual sequence, but what they do, or what they are
for, how they are used, where they are found.
4. [15 pts] Describe the mechanism of DNA replication at
the molecular level. A labeled diagram will help you clarify your
answer. Be sure to include in your description (minimally):
leading and lagging strand - and why these occur; primer - and what it
is for; several different enzymes involved in this process - and
briefly, what they do. This list is NOT complete.
bonus: Write a question that you studied for, and forgetful me, I
neglected to ask. Answer your question. PLEASE ask yourself
something you can answer well! PLEASE answer the question you
actually ask. [up to 5 points awarded based on question &
answer]