MMSC 491 EXAM 1 QUESTIONS WITH VERIFIED
ANSWERS
With reference to aberrant methylation of bases which of the following statements, if
any, is false?
A. S-adenosylmethionine donates methyl groups to a range of different molecules in
cells and frequently inappropriately methylates bases in DNA.
B. Guanine is occasionally methylated to give O-6-methylguanine which base pairs with
adenine rather than with cytidine.
C. In each nucleated cell, about 300-600 adenines are converted to 3-methyladenine
per day.
D. 3-methyladenine can be a cytotoxic base: it distorts the double helix and that can
disrupt crucial DNA-protein interactions. - Answers - B
With reference to base cross-linking, which, if any, of the following statements, is false?
A. Base cross-linking means that covalent bonds form between two bases.
B. The cross-linked bases are on opposing DNA strands.
C. The anti-cancer agent cisplatin causes a type of cross-linking between two guanine
residues.
D. Pyrimidine dimers are a type of base cross-linking that is commonly induced by
excess exposure to sunlight. - Answers - B
Which, if any, of the following statements is false, regarding the sources of genetic
variation?
A. Most of the inherited changes in our DNA arise because of exposure to extracellular
mutagens, including radiation sources and chemical mutagens.
B. Most of the inherited changes in our DNA arise because of unavoidable endogenous
errors in cellular mechanisms and harmful effects of certain natural molecules and
atoms within our cells.
C. Errors in DNA replication and DNA repair are a major source of mutations in our
cells.
D. Significant chemical damage is sustained by DNA because of its proximity to water
molecules in our cells. - Answers - A
Nucleic acid hybridization assays are normally carried out under relaxed hybridization
stringency (to maximize the chances of heteroduplex formation) but afterwards, washes
are carried out that can be designed to favor perfectly matched sequences only by
changing some parameter. Which, if any, of the following changes would be consistent
with that aim?
a) An increase in temperature.
b) An increase in salt concentration.
, c) An increase in the concentration of a polar molecule, such as urea or formamide.
d) Both A and C
E) A, B, and C - Answers - D
Which of the following statements, if any, is false?
A. PCR requires the use of a heat-stable DNA polymerase to make copies of the
template DNA.
B. PCR is usually used to amplify a specific DNA sequence of interest using
C. Oligonucleotide primers that bind to closely flanking sequences.
D. PCR is superior to cell-based DNA cloning for two major reasons: it is much quicker
and it allows much greater DNA amplification. - Answers - D
For many of our genes, the initial RNA transcript needs to be cleaved into pieces. Some
of the pieces, called ____ ____, are discarded, but other alternating pieces called ___
____ are retained and fused in the same linear order as their order when transcribed. -
Answers - introns, exons
Which, if any, of the following statements are false?
a) Constitutive heterochromatin remains highly condensed throughout the cell cycle.
b) Unlike constitutive heterochromatin, facultative heterochromatin describes chromatin
that
can de-condense and behave as euchromatin under certain circumstances.
c) Most of the long arm of the Y chromatin is made up of constitutive heterochromatin.
d) In women one of the two X chromosomes in each diploid cell is heterochromatinised.
e) All of the above are true - Answers - E
Which of the following statements is incorrect?
A. Segregation of mtDNA molecules into daughter cells needs to be equal.
B. The copy number of nuclear DNA molecules is tightly controlled.
C. Hundreds or thousands of mtDNA molecules are found in human cells.
D. The replication of nuclear DNA and mtDNA molecules is not coordinated. - Answers -
A
Which of the following statements is incorrect?
A. Because centromeres and telomeres are critically important for chromosome function
their DNA has been very highly conserved during evolution.
ANSWERS
With reference to aberrant methylation of bases which of the following statements, if
any, is false?
A. S-adenosylmethionine donates methyl groups to a range of different molecules in
cells and frequently inappropriately methylates bases in DNA.
B. Guanine is occasionally methylated to give O-6-methylguanine which base pairs with
adenine rather than with cytidine.
C. In each nucleated cell, about 300-600 adenines are converted to 3-methyladenine
per day.
D. 3-methyladenine can be a cytotoxic base: it distorts the double helix and that can
disrupt crucial DNA-protein interactions. - Answers - B
With reference to base cross-linking, which, if any, of the following statements, is false?
A. Base cross-linking means that covalent bonds form between two bases.
B. The cross-linked bases are on opposing DNA strands.
C. The anti-cancer agent cisplatin causes a type of cross-linking between two guanine
residues.
D. Pyrimidine dimers are a type of base cross-linking that is commonly induced by
excess exposure to sunlight. - Answers - B
Which, if any, of the following statements is false, regarding the sources of genetic
variation?
A. Most of the inherited changes in our DNA arise because of exposure to extracellular
mutagens, including radiation sources and chemical mutagens.
B. Most of the inherited changes in our DNA arise because of unavoidable endogenous
errors in cellular mechanisms and harmful effects of certain natural molecules and
atoms within our cells.
C. Errors in DNA replication and DNA repair are a major source of mutations in our
cells.
D. Significant chemical damage is sustained by DNA because of its proximity to water
molecules in our cells. - Answers - A
Nucleic acid hybridization assays are normally carried out under relaxed hybridization
stringency (to maximize the chances of heteroduplex formation) but afterwards, washes
are carried out that can be designed to favor perfectly matched sequences only by
changing some parameter. Which, if any, of the following changes would be consistent
with that aim?
a) An increase in temperature.
b) An increase in salt concentration.
, c) An increase in the concentration of a polar molecule, such as urea or formamide.
d) Both A and C
E) A, B, and C - Answers - D
Which of the following statements, if any, is false?
A. PCR requires the use of a heat-stable DNA polymerase to make copies of the
template DNA.
B. PCR is usually used to amplify a specific DNA sequence of interest using
C. Oligonucleotide primers that bind to closely flanking sequences.
D. PCR is superior to cell-based DNA cloning for two major reasons: it is much quicker
and it allows much greater DNA amplification. - Answers - D
For many of our genes, the initial RNA transcript needs to be cleaved into pieces. Some
of the pieces, called ____ ____, are discarded, but other alternating pieces called ___
____ are retained and fused in the same linear order as their order when transcribed. -
Answers - introns, exons
Which, if any, of the following statements are false?
a) Constitutive heterochromatin remains highly condensed throughout the cell cycle.
b) Unlike constitutive heterochromatin, facultative heterochromatin describes chromatin
that
can de-condense and behave as euchromatin under certain circumstances.
c) Most of the long arm of the Y chromatin is made up of constitutive heterochromatin.
d) In women one of the two X chromosomes in each diploid cell is heterochromatinised.
e) All of the above are true - Answers - E
Which of the following statements is incorrect?
A. Segregation of mtDNA molecules into daughter cells needs to be equal.
B. The copy number of nuclear DNA molecules is tightly controlled.
C. Hundreds or thousands of mtDNA molecules are found in human cells.
D. The replication of nuclear DNA and mtDNA molecules is not coordinated. - Answers -
A
Which of the following statements is incorrect?
A. Because centromeres and telomeres are critically important for chromosome function
their DNA has been very highly conserved during evolution.
