BIO 230 LATEST 2026 STUDY GUIDE QUESTIONS AND
ANSWERS RATED A+
✔✔at a replication fork, how is the leading strand synthesized - ✔✔continuously
✔✔which of the following does not cause a mutation - ✔✔evolution
✔✔what type of enzyme seals the newly added dna to the rest of the dna molecule -
✔✔ligase
✔✔Using your knowledge of telomerase enzyme and chromosomal size, choose the
statement that correctly describes the information in the figure. - ✔✔Telomerase activity
would solve the end-replication problem, as this enzyme is involved in telomere
lengthening.
✔✔What potential outcomes are possible after replication in a DNA molecule with a
depurination modification that is left unrepaired? - ✔✔The DNA molecule is missing one
nucleotide pair.
The DNA molecule contains the normal sequence.
✔✔what kinds of bonds link the two strands of a double helix to each other -
✔✔hydrogen
✔✔nucleotides in each strand of dna are held together by what type of bonds -
✔✔phosphodiester
✔✔what type of enzyme removes damaged dna from the rest of the dna molecule -
✔✔nuclease
✔✔what type of enzyme fills in the gap after damaged dna has been removed -
✔✔polymerase
✔✔Determine whether the following statement is true or false and why:
Homologous recombination occurs only between DNA molecules that are identical in
nucleotide sequence without any variation. - ✔✔false, because only similar sequence is
needed
✔✔You have joined a lab studying DNA replication in E. coli. The graduate student you
are working with has identified a mutation in primase that makes primase very
inefficient. Your project is to characterize the cells with this mutation. Predict the defects
you would most likely see in the mutant E. coli cells. - ✔✔a delay in DNA polymerase
beginning synthesis
,a longer total time to replicate DNA
✔✔If DNA replication were conservative (although we know it is not), what would
Meselson and Stahl have seen following the first round of replication in E. coli that had
been switched from a heavy (15N-containing) nutrient medium to a light (14N-
containing) nutrient medium? - ✔✔Half the DNA would be heavy, and the other half
would be light.
✔✔To determine if DNA replication is semiconservative, dispersive, or conservative
(see image below), Matt Meselson and Frank Stahl performed a classic experiment in
which they grew E. coli for many generations in a heavy isotope of nitrogen (15N) and
then transferred the bacteria to media containing 14N for a single round of DNA
replication. Density of the DNA was determined via centrifugation and the result of
intermediate density DNA (50% 14N, 50% 15N within a double helix) was consistent
with both semiconservative and dispersive DNA replication. Another round of replication
can discriminate between semiconservative and dispersive DNA replication. What kind
of DNA is expected if these E. coli are grown for a second generation in14N-containing
media? - ✔✔50% intermediate density, 50% light density
✔✔Choose all of the following that correctly describe a characteristic of mismatch
repair. - ✔✔Regions of improper base-pairing between parent and daughter strand are
detected and repaired.
B. Helicase unwinds the DNA in the mismatched area.
C. Exonuclease removes the newly synthesized DNA in the mismatched area.
D. DNA polymerase and ligase fill in the gap.
✔✔Everyone is exposed regularly to ionizing radiation found in the soil, water, and air
and from cosmic rays. In fact, 80% of the ionizing radiation people are exposed to
comes from naturally occurring sources. Ionizing radiation can cause double-strand
breaks in the DNA. Often, the DNA breaks have missing nucleotides at the broken
ends. What type of repair would likely be used, and what would be the result of repairing
this type of damage? - ✔✔Nonhomologous end joining would be used to join the DNA,
but errors would still remain.
✔✔Ionizing radiation can also cause damage to the nitrogenous bases of DNA. Repair
of the damaged bases takes several steps. Which of the following repair mechanisms
can be used to repair the nitrogenous bases of DNA damaged by ionizing radiation? -
✔✔excision repair
✔✔The loss of purine bases from a strand of DNA is typically caused by which of the
following? - ✔✔a spontaneous chemical reaction
,✔✔In the absence of repair, what would the replication of a double helix containing a
mismatch yield? - ✔✔one DNA molecule with the normal sequence and one DNA
molecule with a mutated sequence
✔✔The mismatch repair system recognizes mismatched base pairs, removes a portion
of the DNA strand containing the error, and then resynthesizes the missing DNA using
the correct sequence as a template. But what if the mismatch repair system instead
removed a piece of the DNA strand that contained the correct sequence? What would
replication of this improperly repaired sequence produce? - ✔✔two DNA molecules
bearing the same mutation
✔✔When does homologous recombination most likely occur in order to flawlessly repair
double-stranded DNA breaks? - ✔✔after the cell's DNA has been replicated
✔✔Which of the following occurs when a cell repairs a double-strand DNA break by the
process of nonhomologous end joining? - ✔✔The DNA sequence at the site of repair is
altered by a short deletion.
✔✔The DNA helicase animation shows the bacteriophage T7 helicase unwinding DNA.
Which of the following are critical components of the helicase mechanism of action
necessary to unwind DNA? - ✔✔oscillating loops pulling the single-stranded DNA
through a central hole
B. conformational changes of subunits
C. ATP binding and hydrolysis
✔✔AMP-PNP is a non-hydrolyzable analog of ATP that can bind to proteins in a similar
manner as ATP but is no longer hydrolyzed. Predict what would happen to helicase
activity if AMP-PNP were added to a DNA replication reaction. - ✔✔Helicase would no
longer function, since the AMP-PNP is not hydrolyzed. ATP binding and hydrolysis
induce the conformational changes that facilitate DNA unwinding by helicase.
✔✔What problem with replication of linear chromosomes does telomerase address? -
✔✔The lagging strand stops short of the 3' end during replication, so chromosomes
would shorten in each replication cycle without telomerase.
✔✔Telomerase was first described in the ciliate Tetrahymena thermophila by Elizabeth
Blackburn and her student Carol Greider. They, along with Jack Szostak, subsequently
won a Nobel Prize for this discovery. As the animation shows, the template RNA
sequence in Tetrahymena is 3'-ACCCCAAC-5'. The telomerase protein and RNA
template together extend the 3' end of the chromosome by adding 5'-GGGTTG-3'
repeats to the chromosome. The complementary strand is then synthesized by DNA
polymerase α.
, Blackburn's lab altered the sequence of the telomerase RNA. Predict what might
happen to telomeres in Tetrahymena cells if the Tetrahymena template RNA were
mutated to 3'-ACCCCGAC-5'. - ✔✔Telomere sequence would be altered to 5'-
GGGCTG-3'.
✔✔Predict what might happen to telomeres in Tetrahymena cells if the Tetrahymena
template RNA were mutated from 3'-ACCCCAAC-5' to 3'-AGCCCAAC-5'. -
✔✔Telomeres would become shorter in every generation compared to normal cells.
✔✔Synthetic biologists are trying to create cells from raw material. One step in the
process is encapsulating genetic material into a compartment. Researchers of the origin
of life think that the earliest cells on Earth may have used RNA as their genetic material
instead of DNA. As biologists consider which genetic material to use in creating their
synthetic cells, which of the following characteristics of a single-stranded RNA genome
should they keep in mind? - ✔✔A newly synthesized RNA strand is not identical to the
template strand.
✔✔Which of the following is true for most genes? - ✔✔All of the above are true
regarding genes.
✔✔What is the term that describes the complex of DNA and proteins that makes up a
eukaryotic chromosome? - ✔✔chromatin
✔✔what type of bond connects base pairs - ✔✔hydrogen
✔✔what are the specialized DNA sequences that are at the ends of most eukaryotic
chromosomes called - ✔✔telomeres
✔✔what is the general name given to the most highly condensed form of chromatin -
✔✔heterochromatin
✔✔Which of the statements below is supported by the Avery, McCarty, and MacLeod
experiment and the data in the figure above? - ✔✔DNA from one strain of bacteria can
alter the phenotype of another strain if that DNA is taken up by the other strain.
✔✔which structure is normally on the 5 prime end of a dna strand - ✔✔phosphate group
✔✔determine whether the following statement is true or false: when a cell divides, its
chromatin structure is completely reset - ✔✔false
✔✔in the light microscope, dna molecules are most visible in which of the following -
✔✔in a cell that is dividing
ANSWERS RATED A+
✔✔at a replication fork, how is the leading strand synthesized - ✔✔continuously
✔✔which of the following does not cause a mutation - ✔✔evolution
✔✔what type of enzyme seals the newly added dna to the rest of the dna molecule -
✔✔ligase
✔✔Using your knowledge of telomerase enzyme and chromosomal size, choose the
statement that correctly describes the information in the figure. - ✔✔Telomerase activity
would solve the end-replication problem, as this enzyme is involved in telomere
lengthening.
✔✔What potential outcomes are possible after replication in a DNA molecule with a
depurination modification that is left unrepaired? - ✔✔The DNA molecule is missing one
nucleotide pair.
The DNA molecule contains the normal sequence.
✔✔what kinds of bonds link the two strands of a double helix to each other -
✔✔hydrogen
✔✔nucleotides in each strand of dna are held together by what type of bonds -
✔✔phosphodiester
✔✔what type of enzyme removes damaged dna from the rest of the dna molecule -
✔✔nuclease
✔✔what type of enzyme fills in the gap after damaged dna has been removed -
✔✔polymerase
✔✔Determine whether the following statement is true or false and why:
Homologous recombination occurs only between DNA molecules that are identical in
nucleotide sequence without any variation. - ✔✔false, because only similar sequence is
needed
✔✔You have joined a lab studying DNA replication in E. coli. The graduate student you
are working with has identified a mutation in primase that makes primase very
inefficient. Your project is to characterize the cells with this mutation. Predict the defects
you would most likely see in the mutant E. coli cells. - ✔✔a delay in DNA polymerase
beginning synthesis
,a longer total time to replicate DNA
✔✔If DNA replication were conservative (although we know it is not), what would
Meselson and Stahl have seen following the first round of replication in E. coli that had
been switched from a heavy (15N-containing) nutrient medium to a light (14N-
containing) nutrient medium? - ✔✔Half the DNA would be heavy, and the other half
would be light.
✔✔To determine if DNA replication is semiconservative, dispersive, or conservative
(see image below), Matt Meselson and Frank Stahl performed a classic experiment in
which they grew E. coli for many generations in a heavy isotope of nitrogen (15N) and
then transferred the bacteria to media containing 14N for a single round of DNA
replication. Density of the DNA was determined via centrifugation and the result of
intermediate density DNA (50% 14N, 50% 15N within a double helix) was consistent
with both semiconservative and dispersive DNA replication. Another round of replication
can discriminate between semiconservative and dispersive DNA replication. What kind
of DNA is expected if these E. coli are grown for a second generation in14N-containing
media? - ✔✔50% intermediate density, 50% light density
✔✔Choose all of the following that correctly describe a characteristic of mismatch
repair. - ✔✔Regions of improper base-pairing between parent and daughter strand are
detected and repaired.
B. Helicase unwinds the DNA in the mismatched area.
C. Exonuclease removes the newly synthesized DNA in the mismatched area.
D. DNA polymerase and ligase fill in the gap.
✔✔Everyone is exposed regularly to ionizing radiation found in the soil, water, and air
and from cosmic rays. In fact, 80% of the ionizing radiation people are exposed to
comes from naturally occurring sources. Ionizing radiation can cause double-strand
breaks in the DNA. Often, the DNA breaks have missing nucleotides at the broken
ends. What type of repair would likely be used, and what would be the result of repairing
this type of damage? - ✔✔Nonhomologous end joining would be used to join the DNA,
but errors would still remain.
✔✔Ionizing radiation can also cause damage to the nitrogenous bases of DNA. Repair
of the damaged bases takes several steps. Which of the following repair mechanisms
can be used to repair the nitrogenous bases of DNA damaged by ionizing radiation? -
✔✔excision repair
✔✔The loss of purine bases from a strand of DNA is typically caused by which of the
following? - ✔✔a spontaneous chemical reaction
,✔✔In the absence of repair, what would the replication of a double helix containing a
mismatch yield? - ✔✔one DNA molecule with the normal sequence and one DNA
molecule with a mutated sequence
✔✔The mismatch repair system recognizes mismatched base pairs, removes a portion
of the DNA strand containing the error, and then resynthesizes the missing DNA using
the correct sequence as a template. But what if the mismatch repair system instead
removed a piece of the DNA strand that contained the correct sequence? What would
replication of this improperly repaired sequence produce? - ✔✔two DNA molecules
bearing the same mutation
✔✔When does homologous recombination most likely occur in order to flawlessly repair
double-stranded DNA breaks? - ✔✔after the cell's DNA has been replicated
✔✔Which of the following occurs when a cell repairs a double-strand DNA break by the
process of nonhomologous end joining? - ✔✔The DNA sequence at the site of repair is
altered by a short deletion.
✔✔The DNA helicase animation shows the bacteriophage T7 helicase unwinding DNA.
Which of the following are critical components of the helicase mechanism of action
necessary to unwind DNA? - ✔✔oscillating loops pulling the single-stranded DNA
through a central hole
B. conformational changes of subunits
C. ATP binding and hydrolysis
✔✔AMP-PNP is a non-hydrolyzable analog of ATP that can bind to proteins in a similar
manner as ATP but is no longer hydrolyzed. Predict what would happen to helicase
activity if AMP-PNP were added to a DNA replication reaction. - ✔✔Helicase would no
longer function, since the AMP-PNP is not hydrolyzed. ATP binding and hydrolysis
induce the conformational changes that facilitate DNA unwinding by helicase.
✔✔What problem with replication of linear chromosomes does telomerase address? -
✔✔The lagging strand stops short of the 3' end during replication, so chromosomes
would shorten in each replication cycle without telomerase.
✔✔Telomerase was first described in the ciliate Tetrahymena thermophila by Elizabeth
Blackburn and her student Carol Greider. They, along with Jack Szostak, subsequently
won a Nobel Prize for this discovery. As the animation shows, the template RNA
sequence in Tetrahymena is 3'-ACCCCAAC-5'. The telomerase protein and RNA
template together extend the 3' end of the chromosome by adding 5'-GGGTTG-3'
repeats to the chromosome. The complementary strand is then synthesized by DNA
polymerase α.
, Blackburn's lab altered the sequence of the telomerase RNA. Predict what might
happen to telomeres in Tetrahymena cells if the Tetrahymena template RNA were
mutated to 3'-ACCCCGAC-5'. - ✔✔Telomere sequence would be altered to 5'-
GGGCTG-3'.
✔✔Predict what might happen to telomeres in Tetrahymena cells if the Tetrahymena
template RNA were mutated from 3'-ACCCCAAC-5' to 3'-AGCCCAAC-5'. -
✔✔Telomeres would become shorter in every generation compared to normal cells.
✔✔Synthetic biologists are trying to create cells from raw material. One step in the
process is encapsulating genetic material into a compartment. Researchers of the origin
of life think that the earliest cells on Earth may have used RNA as their genetic material
instead of DNA. As biologists consider which genetic material to use in creating their
synthetic cells, which of the following characteristics of a single-stranded RNA genome
should they keep in mind? - ✔✔A newly synthesized RNA strand is not identical to the
template strand.
✔✔Which of the following is true for most genes? - ✔✔All of the above are true
regarding genes.
✔✔What is the term that describes the complex of DNA and proteins that makes up a
eukaryotic chromosome? - ✔✔chromatin
✔✔what type of bond connects base pairs - ✔✔hydrogen
✔✔what are the specialized DNA sequences that are at the ends of most eukaryotic
chromosomes called - ✔✔telomeres
✔✔what is the general name given to the most highly condensed form of chromatin -
✔✔heterochromatin
✔✔Which of the statements below is supported by the Avery, McCarty, and MacLeod
experiment and the data in the figure above? - ✔✔DNA from one strain of bacteria can
alter the phenotype of another strain if that DNA is taken up by the other strain.
✔✔which structure is normally on the 5 prime end of a dna strand - ✔✔phosphate group
✔✔determine whether the following statement is true or false: when a cell divides, its
chromatin structure is completely reset - ✔✔false
✔✔in the light microscope, dna molecules are most visible in which of the following -
✔✔in a cell that is dividing
