BIOC 384 EXAM 4 QUESTIONS WITH VERIFIED
ANSWERS
If 15N DNA (heavy) replicated using conservative replication in 14N (light) media, the
outcome would be different than semi-conservative replication, and in this case, the two
daughter DNA double strands would be ______________after one generation. -
Answers - Heavy only for one daughter DNA and light only for the other daughter DNA
Prokaryotic and eukaryotic DNA polymerases rarely make mismatched base pairs
because ____________. - Answers - The active site does not fit mismatches well
Why do helicase and gyrase need to work together to keep the replication fork moving
forward? - Answers - Helicase unwinds the DNA and gyrase relieves the torsional strain
created by the unwinding
The Tus-Ter complex terminates E. coli DNA synthesis by ____________. - Answers -
Blocking the opening of the DNA helix at the fork by helicase
The Ames test is designed to identify mutation rates using a strategy based on
___________. - Answers - The frequency of new mutations that compensate for an
existing mutation.
Individuals with mutations of BRCA have increased incidence of cancer because of
their___________. - Answers - Decreased ability to repair double-strand DNA breaks
A Holliday junction can best be defined as a region of ________________. - Answers -
A quadruplex DNA structure
Lysogeny by bacteriophages causes what result to the host DNA? - Answers -
Integration of virus DNA into host DNA
How are RNA tertiary structures different from protein tertiary structures? - Answers -
RNA adopts multiple structures, whereas protein structures are restricted.
Long noncoding RNA (lncRNA) is generated from _____________. - Answers - The
transcription of genomic DNA
How do bacterial sigma factor proteins promote RNA synthesis? - Answers - They
recruit RNA polymerase to specific sequences at the 5' end of genes.
,In which direction is mRNA synthesized by prokaryotic and eukaryotic RNA
polymerases? - Answers - The mRNA is synthesized with the 5' to 3' phosphodiester
linkages.
The spliceosome _____ - Answers - Resembles group II introns in its mechanism and
product.
A common chemical modification found in RNA is _____ - Answers - Methylation of
nucleotide bases in tRNA
Identify one way in which RNA splicing can give rise to multiple mRNA transcripts from
a gene containing 3 exons and 2 introns - Answers - Splicing between the 3' end of
exon 1 and 5' end of exon 3
The enzyme responsible for generating siRNA from double strand RNA is ____ -
Answers - Dicer
In an iteration of the Nirenberg-Leder experiment to assign triplet codons to specific
amino acids, radioactively labeled aminoacyl-tRNA with the anticodon of 3'-CUG-5' was
retained on the filter at the end of the experiment. Which mRNA was used in this
iteration of the experiment? - Answers - 5'-GAC-3'
Which base location in the figure below (A, B, C, D) explains the wobble hypothesis? -
Answers - 5' end
Aminoacyl-tRNA synthetases carry out editing _____ - Answers - At a site that is distinct
from the active site
A common feature of protein synthesis in both eukaryotes and prokaryotes is _____ -
Answers - Hydrolysis of GTP to facilitate binding of the AA-tRNA^AA
What step in the process of translation of a nascent protein into the lumen of the ER
requires hydrolysis of GTP? - Answers - Transfer of the signal peptide sequence into
the translocon
In the ER, prenylation can occur. Prenylation is the attachment of an isoprenoid group
to a _____ residue via a(n) _____ - Answers - Cysteine; thioester
Which of the following statements best describes how the terms trans-acting and cis-
acting apply to gene regulation? - Answers - Trans-acting factors are proteins that bind
to specific DNA sequences, which are themselves cis-acting sites in DNA
When there are high levels of tryptophan in the bacterial cell, the effect it has on the Trp
repressor is _____ and the effect on the structure of the Trp operon mRNA is _____ -
Answers - To stimulate operon binding; to promote formation of the regions 3-4 stem
loop
, One function of eukaryotic transcriptional activator proteins is to _____ - Answers -
Recruit chromatin modifying proteins such as HAT and HDAC enzymes
What are the three molecular processes that are required to convert a skin cell into an
induced pluripotent stem cell after introduction of the four transcription factor genes? -
Answers - The Sox2/Oct4/Nanog complex inhibits expression of cell differentiating
genes
The Sox2/Oct4/Nanog complex activates expression of stem cell genes
The Sox2/Oct4/Nanog complex activates a positive autoregulatory loop
Answer the following True/False questions regarding the inheritance of hMLH1
mutations in Lynch Syndrome patients and the effect of these mutations on the
frequency of specific cancers.
T/F: A child has 25% chance of having Lynch Syndrome if one parent has Lynch
Syndrome
T/F: Endometrial cancer occurs ~100 times more frequently in women with Lynch
Syndrome by the age of 50 than it does in women in the general population by age 50.
T/F: For every ~100 patients with Lynch Syndrome who are diagnosed with stomach
cancer there are ~8 patients in the general population who will also be diagnosed with
stomach cancer.
T/F: A child has a 50% chance of having Lynch Syndrome if both parents have Lynch
Syndrome.
T/F: Colon cancer frequency in Lynch Syndrome patients is ~40 times higher by age 70
compared to the frequency of colon cancer by age 70 in the general population.
T/F: For every 25 patients in the general population di - Answers - F, T, T, F, T, F
What is the difference between a somatic mutation and a germline mutation? - Answers
- Somatic mutations occur during a lifetime and are not inherited; germline mutations
exist in gametes and are inherited by offspring
When using the Ames test to determine if a compound is mutagenic, it is often added to
a rat liver extract and incubated overnight before putting the mixture onto filter paper in
a media plate of His- bacteria.
a) What would it mean if fewer colonies were observed on the plate if the compound
were first treated with rat liver extract as compared to not treating the compound?
b) What would it mean if more colonies were observed on the plate if the compound
were first treated with rat liver extract as compared to not treating the compound? -
Answers - a) If fewer colonies were observed, then enzymes in the rat liver extract
modified the compound to make it less potent.
b) If more colonies were observed, then enzymes in the rat liver extract modified the
compound to make it more potent.
ANSWERS
If 15N DNA (heavy) replicated using conservative replication in 14N (light) media, the
outcome would be different than semi-conservative replication, and in this case, the two
daughter DNA double strands would be ______________after one generation. -
Answers - Heavy only for one daughter DNA and light only for the other daughter DNA
Prokaryotic and eukaryotic DNA polymerases rarely make mismatched base pairs
because ____________. - Answers - The active site does not fit mismatches well
Why do helicase and gyrase need to work together to keep the replication fork moving
forward? - Answers - Helicase unwinds the DNA and gyrase relieves the torsional strain
created by the unwinding
The Tus-Ter complex terminates E. coli DNA synthesis by ____________. - Answers -
Blocking the opening of the DNA helix at the fork by helicase
The Ames test is designed to identify mutation rates using a strategy based on
___________. - Answers - The frequency of new mutations that compensate for an
existing mutation.
Individuals with mutations of BRCA have increased incidence of cancer because of
their___________. - Answers - Decreased ability to repair double-strand DNA breaks
A Holliday junction can best be defined as a region of ________________. - Answers -
A quadruplex DNA structure
Lysogeny by bacteriophages causes what result to the host DNA? - Answers -
Integration of virus DNA into host DNA
How are RNA tertiary structures different from protein tertiary structures? - Answers -
RNA adopts multiple structures, whereas protein structures are restricted.
Long noncoding RNA (lncRNA) is generated from _____________. - Answers - The
transcription of genomic DNA
How do bacterial sigma factor proteins promote RNA synthesis? - Answers - They
recruit RNA polymerase to specific sequences at the 5' end of genes.
,In which direction is mRNA synthesized by prokaryotic and eukaryotic RNA
polymerases? - Answers - The mRNA is synthesized with the 5' to 3' phosphodiester
linkages.
The spliceosome _____ - Answers - Resembles group II introns in its mechanism and
product.
A common chemical modification found in RNA is _____ - Answers - Methylation of
nucleotide bases in tRNA
Identify one way in which RNA splicing can give rise to multiple mRNA transcripts from
a gene containing 3 exons and 2 introns - Answers - Splicing between the 3' end of
exon 1 and 5' end of exon 3
The enzyme responsible for generating siRNA from double strand RNA is ____ -
Answers - Dicer
In an iteration of the Nirenberg-Leder experiment to assign triplet codons to specific
amino acids, radioactively labeled aminoacyl-tRNA with the anticodon of 3'-CUG-5' was
retained on the filter at the end of the experiment. Which mRNA was used in this
iteration of the experiment? - Answers - 5'-GAC-3'
Which base location in the figure below (A, B, C, D) explains the wobble hypothesis? -
Answers - 5' end
Aminoacyl-tRNA synthetases carry out editing _____ - Answers - At a site that is distinct
from the active site
A common feature of protein synthesis in both eukaryotes and prokaryotes is _____ -
Answers - Hydrolysis of GTP to facilitate binding of the AA-tRNA^AA
What step in the process of translation of a nascent protein into the lumen of the ER
requires hydrolysis of GTP? - Answers - Transfer of the signal peptide sequence into
the translocon
In the ER, prenylation can occur. Prenylation is the attachment of an isoprenoid group
to a _____ residue via a(n) _____ - Answers - Cysteine; thioester
Which of the following statements best describes how the terms trans-acting and cis-
acting apply to gene regulation? - Answers - Trans-acting factors are proteins that bind
to specific DNA sequences, which are themselves cis-acting sites in DNA
When there are high levels of tryptophan in the bacterial cell, the effect it has on the Trp
repressor is _____ and the effect on the structure of the Trp operon mRNA is _____ -
Answers - To stimulate operon binding; to promote formation of the regions 3-4 stem
loop
, One function of eukaryotic transcriptional activator proteins is to _____ - Answers -
Recruit chromatin modifying proteins such as HAT and HDAC enzymes
What are the three molecular processes that are required to convert a skin cell into an
induced pluripotent stem cell after introduction of the four transcription factor genes? -
Answers - The Sox2/Oct4/Nanog complex inhibits expression of cell differentiating
genes
The Sox2/Oct4/Nanog complex activates expression of stem cell genes
The Sox2/Oct4/Nanog complex activates a positive autoregulatory loop
Answer the following True/False questions regarding the inheritance of hMLH1
mutations in Lynch Syndrome patients and the effect of these mutations on the
frequency of specific cancers.
T/F: A child has 25% chance of having Lynch Syndrome if one parent has Lynch
Syndrome
T/F: Endometrial cancer occurs ~100 times more frequently in women with Lynch
Syndrome by the age of 50 than it does in women in the general population by age 50.
T/F: For every ~100 patients with Lynch Syndrome who are diagnosed with stomach
cancer there are ~8 patients in the general population who will also be diagnosed with
stomach cancer.
T/F: A child has a 50% chance of having Lynch Syndrome if both parents have Lynch
Syndrome.
T/F: Colon cancer frequency in Lynch Syndrome patients is ~40 times higher by age 70
compared to the frequency of colon cancer by age 70 in the general population.
T/F: For every 25 patients in the general population di - Answers - F, T, T, F, T, F
What is the difference between a somatic mutation and a germline mutation? - Answers
- Somatic mutations occur during a lifetime and are not inherited; germline mutations
exist in gametes and are inherited by offspring
When using the Ames test to determine if a compound is mutagenic, it is often added to
a rat liver extract and incubated overnight before putting the mixture onto filter paper in
a media plate of His- bacteria.
a) What would it mean if fewer colonies were observed on the plate if the compound
were first treated with rat liver extract as compared to not treating the compound?
b) What would it mean if more colonies were observed on the plate if the compound
were first treated with rat liver extract as compared to not treating the compound? -
Answers - a) If fewer colonies were observed, then enzymes in the rat liver extract
modified the compound to make it less potent.
b) If more colonies were observed, then enzymes in the rat liver extract modified the
compound to make it more potent.
