How is the Ames test used to quantitate mutagenic potential of chemical compounds? Select the TWO best answers. correct answers The Salmonella test strain used in the Ames test contains a mutation in the histidine biosynthetic pathway, which is used to identify compounds that induce back mutations ...
BIOC 385 Exam 4 || A+ Graded Already.
How is the Ames test used to quantitate mutagenic potential of chemical compounds? Select the
TWO best answers. correct answers The Salmonella test strain used in the Ames test contains a
mutation in the histidine biosynthetic pathway, which is used to identify compounds that induce
back mutations to permit bacterial growth on histidine free plates.
The chemical compound to be tested is added to a filter paper disk and placed on agar plates
containing the tester Salmonella strain; potent mutagens result in MORE colonies forming on
histidine free plates as compared to control plates.
What is a Holliday Junction? Choose the one BEST answer below. correct answers The location
in a DNA recombination intermediate where DNA strands from different DNA molecules are
crossed over, which links the two DNA molecules together.
The processes of DNA replication and RNA transcription in E. coli are similar in some respects
and different in others.
Select the THREE statements below that describe BOTH DNA replication and RNA
transcription in E. coli. correct answers The direction of polymerization is 5' to 3'
A specific region of the DNA is recognized and bound by the polymerase.
The direction of enzyme movement on the template strand is 3' to 5'
Match the name of the DNA repair mechanism with the correct description. correct answers
mismatch-Functions with DNA replication to remove incorrect nucleotides from the nascent
strand.
base excision repair-Requires an endonuclease to remove an abasic nucleotide before DNA Pol I
can replace a portion of the strand.
nucleotide excision repair-Is needed to repair chemical damage in DNA effecting more than one
nucleotide, such as cyclobutane pyrimidine dimers.
direct repair-Repairs nucleotide bases without requiring DNA ligase.
What accounts for the high fidelity of DNA polymerization? Choose the ONE best answer.
correct answers Active site geometry ensures that only correct sized nucleotide base pairs are
formed, and 3' to 5' proofreading removes incorrect nucleotides.
What is the function of the MutS-MutL-MutH protein complex? correct answers None of these
answers are correct.
If 15N DNA replicated using conservative replication in 14N media, the outcome would be that
new DNA has correct answers one high density and one low density strand
,In the figure show below of an E. coli replication fork, which protein is responsible for relieving
torsional stress? correct answers Gyrase
Helicase is responsible for unwinding the DNA duplex for replication. This action leads to
torsional strain upstream of the replication fork, which would inhibit forward movement of the
fork. Gyrase, which is a type II topoisomerase, relieves this strain.
Based on the figure below, cleavage followed by rejoining at which sites would lead to no
recombination or loss of genetic information? correct answers 1 and 3
AZT is such a good HIV drug because it correct answers prevents new DNA from being
replicated.
Which of the following is correct concerning self-splicing introns? correct answers None of these
answers are correct
What effect is likely from the alteration of the sequence at the 5' end of the RNA component of
the U1 snRNP from 5'AUACYYACCU3" to 5'AUACYYGCCU3'? (Note that Y in the sequence
stands for the modified base "psi") Choose the ONE best choice from the list below. correct
answers The 5' splicing junction that will be recognized by this altered spliceosome will be
5'AGGCAGGU3' because the nucleotide sequence of the base pairing portion of U1 snRNP has
changed.
Francis Crick hypothesized that the Genetic Code must require 3 nucleotides in the mRNA to
specify each amino acid based on a simple calculation. What was the logic behind this
calculation? Choose the ONE best answer. correct answers Based on the number of known
amino acids and the number of known nucleotide bases.
What explains the observation that a single eukaryotic protein coding gene can give rise to
multiple different proteins, i.e., why are there only ~25,000 human genes in the genome, but
~150,000 different proteins in the human "proteome?" Choose the TWO best correct answers.
correct answers mRNA transcripts from the same gene can be differentially spliced to
include/exclude exons.
Genes can contain more than one polyadenylation site, which alters the 3' of the mRNA
transcript and the inclusion/exclusion of exons.
The processes of DNA replication and RNA transcription in E. coli are similar in some respects
and different in others.
Select the THREE statements below that describe BOTH DNA replication and RNA
transcription in E. coli. correct answers The direction of enzyme movement on the template
strand is 3' to 5'
, The direction of enzyme movement on the template strand is 3' to 5'
A specific region of the DNA is recognized and bound by the polymerase.
Why does RNA contain uracil and DNA contain thymine? Choose the ONE best answer to this
question. correct answers None of these statements are correct.
Nirenberg and colleagues determined a portion of the genetic code using filter binding assays
that included ribosomes, trinucleotides and tRNA molecules charged with radioactively-labeled
amino acids. Choose the answer below that correctly answers the following three questions in
order:
1) If the trinucleotide sequence is CAG, which amino acid will be bound to the filter paper?
2) If the wobble position of the trinucleotide sequence is changed to a U, which amino acid will
be bound to the filter paper?
3) True or False: Two distinct tRNA molecules with different anticodon sequences MUST be
used to recognize the codons AGA and AGG. correct answers 1) Gln, 2) His, 3) False
The Shine-Dalgarno sequence of mRNA base pairs with the __________ rRNA within the
prokaryote __________ ribosomal subunit. correct answers 16S; 30S
The initiation, elongation, and termination of eukaryotic transcription is controlled by the correct
answers extent of phosphorylation and dephosphorylation of the RNA polymerase CTD.
If the following mRNA was added to a cell-free translation system, how many unique protein
sequences would be generated?
ACCACCACCACCACCACCACCACCACCACCACCACCACCACC correct answers 3
When lactose levels in the environment are low, transcription of the lac operon correct answers
decreases
The correct mRNA secondary structure of transcriptional termination is __________ stem-loop
structure. correct answers 3-4
Which of the following best describes how trans- and cis-acting factors operate? correct answers
Trans-acting factors can bind to specific DNA sequences whereas cis-acting sites are DNA
sequences.
What function do HAT and HDAC perform in the chromatin-modifying process? correct
answers HAT activates the gene and HDAC represses the gene.
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