Chapter 14
E coli polymerases have __ to __ exonuclease activity
3 5
DNA polymerases use their ________ activity to remove a mismatched basepair. -3' -> 5' exonuclease -5' -> 3' exonuclease -RNase -protease -mismatchase
3' -> 5' exonuclease
DNA is synthesized from __ to __
5 3
What DNA sequences is complementary to 5' ATGGTCAGT 3'? 5' TGACTGGTA 3' 5' ACTGACCAT 3' 5' TACCAGTCA 3' 5' ATGGTCAGT 3'
5' ACTGACCAT 3'
Chargaff's rules for the pairing of nitrogen bases is A = G and C = T. A = C and G = T. A+T = G+C. A = T and G = C.
A = T and G = C.
Endonucleases and exonucleases are enzymes that can remove nucleotides from a polynucleotide chain. Where do endonucleases and exonucleases remove nucleotides from? -An endonuclease removes nucleotides from the ends of the chain; an exonuclease removes nucleotides internally. -An endonuclease removes nucleotides from the 3' end of the chain; an exonuclease removes nucleotides from the 5' end of the chain. -An endonuclease removes nucleotides from the 5' end of the chain; an exonuclease removes nucleotides from the 3' end of the chain. -An endonuclease removes nucleotides interally; an exonuclease removes nucleotides from the ends of the chain.
An endonuclease removes nucleotides interally; an exonuclease removes nucleotides from the ends of the chain.
Why is the lagging strand synthesized in a discontinuous fashion? -The lagging strand is complementary to the leading strand -DNA synthesis must occur in a 5' to 3' direction, which imposes spatial constraints on the synthesis of the lagging strand -The DNA polymerase enzyme that synthesizes the lagging strand can only synthesize short sequences of DNA before it falls off the template -The template of the lagging strand is discontinuous -All of these are reasons why the lagging strand is synthesized in a discontinuous fashion
DNA synthesis must occur in a 5' to 3' direction, which imposes spatial constraints on the synthesis of the lagging strand
Load cohesin complexes to chromatin
G1
MPF initiates breakdown of nuclear envelope allowing us to pass through which checkpoint?
G2
When is the highest concentration of cyclin?
G2
Where is cyclin highest?
G2 and G1 checkpoints
Which of the following best describes the function of telomerase at the telomere? -It makes special primers that do not need to be removed. -It synthesizes new DNA without the use of a template. -It adds new DNA to both strands of the telomere overhang. -It adds new DNA to the shorter strand of the telomere overhang. -It adds new DNA to the longer strand of the telomere overhang.
It adds new DNA to the longer strand of the telomere overhang.
You decide to repeat the Meselson-Stahl experiment, except this time you plan to grow the E. coli cells on light 14N medium for many generations and then transfer them to heavy 15N medium and allow them to grow for 2 additional generations (2 rounds of DNA replication). If the conservative model of DNA replication is correct, what is the expected distribution of DNA in the density gradient after one round of replication? -One band of light density -One band of heavy density -One band of intermediate density -One band of light density and one band of heavy density -One band of light density and one band of intermediate density
One band of light density and one band of heavy density
acts on lagging strand to remove primers and replace with DNA
Pol I
main replication enzyme; DNA synthesis
Pol III
Before DNA polymerase III can begin assembling new DNA nucleotides, which of the following must occur? -DNA polymerase III adds deoxyribonucleotides. -DNA polymerase I removes some material and replaces it with DNA. -Phosphodiester bonds must be broken between the two strands of DNA. -DNA ligase forms a phosphodiester bond between the 3' OH of the growing strand and the 5' phosphate in front of it. -RNA primase constructs a short RNA primer.
RNA primase constructs a short RNA primer.
During DNA replication, each new strand begins with a short RNA primer. lipid primer. amino acid primer. hydrophilic primer. DNA primer.
RNA primer
New mixtures of parental and synthesized strands
dispersive model
Cells that divide frequently tend to have relatively low levels of telomerase t/f
false
During embryonic and childhood development in humans, telomerase activity is relatively low compared to the level of activity in most somatic cells of an adult. t/f
false
Error correcting mechanisms during DNA replication cause cells to accumulate errors at a higher rate, which leads to higher levels of deleterious or lethal mutations. t/f
false
The activity of telomerase in most mature somatic cells is kept high by increasing the expression of the gene encoding this enzyme t/f
false
When telomerase is added to cells grown in culture, their lifespan decreases relative to controls that have no telomerase added. t/f
false
The enzyme that unwinds a segment of the DNA molecule is... -DNA polymerase. -DNA ligase. -RNA primase. -DNA polymerase III. -helicase.
helicase
unwinds the double helix
helicase
enzymes that use energy from ATP to unwind the DNA template
helicases
3 end of DNA has _________
hydroxyl
You are asked to participate in a clinical trial for a new drug that can activate telomerase. What would be a likely risk of taking such a drug? -Increased vulnerability to cancer -Decreased telomere length -Premature aging -Decreased capacity for tissue repair
increased vulnerability to cancer
What is the correct sequence for DNA replication in E. coli? -initiation, elongation, termination -initiation, termination, elongation -elongation, initiation, termination -elongation, termination, initiation
initiation, elongation, termination
Does a negative or positive signal ensure that all kinetochores have a microtubule attached?
negative
Building block needed to assemble a new DNA molecule
nucleoside triphosphate
Serves as a template for a new DNA molecule
parental DNA
If 35S was found in progeny phages rather than 32P, Hershey and Chase would have concluded that -proteins contain phosphorus. -DNA contains sulfur. -phage DNA enters the host cell. -phage protein enters the host cell. -phage can kill the E. coli cell.
phage protein enters the host cell.
5 end of DNA has ________
phosphate
Kinase adds a __________.
phosphate
Every DNA and RNA has ___________
polarity
Which enzyme adds new nucleotides to the end of a growing strand? Polymerase Helicase Gyrase Endonuclease Ligase
polymerase
synthesizes RNA primers
primase
When does the nuclear envelope breakdown?
prophase
Replication of DNA is dispersive. semiconservative. conservative. redundant. semidispersive.
semiconservative
-one strand parental duplex remains intact with daughter strands -new complementary strand built for each parental strand consisting of new nucleotides -daughter strand has one parent strand and one newly synthesized strand
semiconservative model
C/G forms ___ H bonds
three
enzymes that can alter the topological state of DNA
topoisomerases
Mice with low telomerase activity appear to be normal for up to six generations, but they show steadily decreasing telomere length that eventually leads to nonviable offspring t/f
true
With each cell division, chromosomes gradually shorten in the absence of telomerase activity. t/f
true
If 28% of the nucleotides in a DNA molecule contain the base T, what percent will contain the base G? Enter your answer as a whole number without the percent sign
22
Evaluate the statements below and determine which is the best explanation for why bacteria don't use telomerase. -Telomerase did not evolve in the prokaryotic lineages. -Bacteria have an extremely short life span, so they do not need to worry about their chromosomes shortening. -Bacteria have circular chromosomes that do not shorten. -Bacteria use a different enzyme that carries out the same function as telomerase. -None of these adequately explain why bacteria do not use telomerase.
Bacteria have circular chromosomes that do not shorten.
Avery and his coworkers showed that the agent responsible for changing nonvirulent bacteria into virulent bacteria was RNA. lipid. protein. polysaccharide. DNA.
DNA
This is the genetic material for all cellular organisms and some viruses. DNA RNA Protein Chromatin
DNA
What part of the phage entered the bacterial cell following infection? DNA RNA protein coat the entire phage no part
DNA
As the two strands of DNA are unraveled, which enzyme relieves the strain on the two strands? DNA exonuclease DNA gyrase DNA ligase DNA endonuclease DNA polymerase
DNA gyrase
relieves torque
DNA gyrase
joins the ends of DNA segments; DNA repair
DNA ligase
Adds new bases to 3' end
DNA polymerase
Matches DNA to complementary base and links nucleotides
DNA polymerase
Which of the following synthesizes the daughter strands during DNA replication? -DNA primase -helicase -RNA polymerase -DNA polymerase -topoisomerase
DNA polymerase
During DNA replication, which enzyme removes the RNA primers and then fills in the gap? DNA primase DNA ligase DNA polymerase III DNA polymerase I
DNA polymerase I
erases primer and fills gaps
DNA polymerase I
synthesizes DNA
DNA polymerase III
The enzyme that travels along the leading strand assembling new nucleotides on a growing new strand of DNA is... -DNA polymerase. -DNA ligase. -RNA primase. -DNA polymerase III. -helicase.
DNA polymerase.
Which of the following statements regarding the repair of thymine dimers is TRUE? -Repair of thymine dimers requires the presence of light as an energy source for repair. -Repair of thymine dimers prevents DNA replication or transcription from occurring. -Excision repair of thymine dimers is possible because there are two strands of DNA. -Light Repair of thymine dimers prevents future dimers from forming in the same region of DNA.
Excision repair of thymine dimers is possible because there are two strands of DNA.
Telomerase is a potential drug target for treating cancer. Therapies in development focus on telomerase inhibition. What is a possible concern if a telomerase inhibitor is administered systemically to a cancer patient? Normal cells such as hepatocytes or neurons would likely be affected by this drug. If the patient is a child, most of their normal cells would likely be affected by this drug. Inhibiting telomerase is likely to be causative of cancer. Inhibiting telomerase would likely increase the lifespan of cancer cells.
If the patient is a child, most of their normal cells would likely be affected by this drug.
replication fork
S
____ coats single strands after helicases come through
SSB
If an organism had a DNA polymerase III that lost its ability to proofread, which of the following statements would be TRUE? -DNA could not be synthesized, and the organism would die. -DNA polymerase III would randomly add new nucleotides, and the entire sequence of new DNA would be worthless. The organism would die. -The mutation rate for the organism would increase, and more substitutions would be seen in its DNA than in an organism that had functional proofreading. -The proofreading ability of RNA polymerase would restore the lost proofreading ability of the DNA polymerase III, and the organism would be normal. -DNA Polymerase I would take over the function of DNA Polymerase III, and the organism would be normal.
The mutation rate for the organism would increase, and more substitutions would be seen in its DNA than in an organism that had functional proofreading.
An organism has a mutation in its telomerase, so that the RNA template is 3' AAACCCCAAC 5' rather than the normal 3' AACCCCAAC 5'. What is the most likely effect this mutation will have on the organism. -The organism will develop abnormally, because this mutation introduces a frame shift. -The organism will die early because its telomeres will shorten with every round of mitosis. -The organism will only be slightly effected because the mutation will result in only a single amino acid substitution. -The organism will not be effected because the telomerase will still function to keep its telomeres long. -The organism will develop abnormally, because this mutation introduces a frame shift AND it will die early because its telomeres will shorted with every round of mitosis.
The organism will not be effected because the telomerase will still function to keep its telomeres long.
What might be the consequence of an organism that was born without functional telomerase? -The organism would not be able to properly replicate its DNA and it would die. -The organism would not be able to properly synthesize proteins and it would die. -The organism would have shorter chromosomes with every round of mitosis, which would eventually result in cells that were unable to properly function and it would die. -The organism would have shorter chromosomes with every round of mitosis, but it would only lose DNA in the telomeric repeat region, so it would live a normal life span. -The organism would have chromosomes that fuse together and would not be capable of proper mitosis, so it would die.
The organism would have shorter chromosomes with every round of mitosis, which would eventually result in cells that were unable to properly function and it would die.
Which of the following is NOT a mechanism that cells use to ensure their DNA is accurately replicated? -Hydrogen bonding across the double helix is more stable when nucleotides abide by Chargoff's rules -DNA polymerase will not catalyze the phosphodiester bond if a mismatched nucleotide enters the active site -When mismatched nucleotides are detected, DNA polymerase will begin to synthesize DNA in the 3' to 5' direction to correct the mistake -DNA polymerase can identify mismatched nucleotides and use its 3' to 5' exonuclease activity to remove a small section of DNA that includes the mutation -All of these are mechanisms that cells have to ensure the fidelity of DNA replication.
When mismatched nucleotides are detected, DNA polymerase will begin to synthesize DNA in the 3' to 5' direction to correct the mistake
Telomerase is unique enzyme because it contains -a DNA molecule. -an RNA molecule. -amino acids. -a DNA binding site. -both DNA and RNA molecules.
an RNA molecule
Active only when bound to cyclin. Add to proteins. Phosphorylates
cdk
_________ keep sister chromatids together
cohesins
Either strand of a DNA molecule can be used as a template to reconstruct the other because the two strands of a DNA molecule are ________ . complementary antiparallel identical bound
complementary
-both strands parental duplex remain intact -both strands new DNA duplex would contain all new nucleotides
conservative model
UV light damages DNA by causing -covalent bonds to form between two cytosines next to each other on the same DNA strand. -covalent bonds to form between thymine nucleotides next to each other on the same DNA strand. -covalent bonds to form between two thymine nucleotides on opposing DNA strands. -covalent bonds to form between a thymine and an adenine on the same DNA strand.
covalent bonds to form between thymine nucleotides next to each other on the same DNA strand.
The lagging strand is replicated with a series of Okazaki fragments and that is why its synthesis is considered to be discontinuous. bidirectional. antiparallel. semiconservative. continuous.
discontinuous
"Proofreading" effectively eliminates all errors during DNA replication. t/f
false
Any agent that decreases the number of mutations below background levels is called a mutagen. t/f
false
Cells cannot escape exposure to mutagens, but they have evolved systems that enable them to repair all of the damage. t/f
false
Griffith, a British microbiologist, used bacteria and mice to demonstrate the process of transformation. During transformation, -genetic material is transferred from one bacterial cell to another. -a bacterial chromosome produces an exact copy of itself. -the nucleus of a mouse cell repairs itself when damaged by bacterial infection. -DNA from an infected mouse cell changes bacteria from a non-pathogenic to a pathogenic form. -a bacterial cell is transformed into a spore during unsuitable environmental conditions.
genetic material is transferred from one bacterial cell to another.
Information obtained by Franklin from X-ray crystallography on DNA suggested that it is shaped like a -ribbon. -hollow cylinder. -icosahedron. -pleated sheet. -helix.
helix
After attaching to a bacterial cell, a bacteriophage typically -injects DNA into the cell. -injects protein into the cell. -transforms the cell into a virulent strain. -extracts protein from the cell. -extracts DNA from the cell.
injects DNA into the cell.
An enzyme that transfers a phosphate group from ATP to a protein would be called ___________.
kinase
What microtubules attach to
kinetochore
What keeps the nuclear envelope ?
lamins
The ___________ model of DNA replication requires parental DNA, enzymes to do copying, and nucleotides
semiconservative
stabilizes single-stranded regions
single-strand binding protein
Which types of adult human cells are likely to be created by mitosis?
skin cells, blood cells, neurons
There are _______ forms of bases
tautomeric
Without the aid of telomerase, DNA polymerases cannot replicate -the 5' end of circular chromosomes. -the 3' end of circular chromosomes. -the 5' end of linear chromosomes. -the 3' end of linear chromosomes. -both the 5' and 3' ends of linear chromosomes.
the 3' end of linear chromosomes.
After a long week of sunbathing on the beach, what type of DNA damage should you be most concerned about? -thymine dimers -photolyase-induced mutations -decreased telomere length -activation of uvr A, B, and C genes
thymine dimers
Which of the following prevents supercoiling of the DNA strands ahead of the replication bubble? -helicase -topoisomerase -DNA binding proteins -DnaA -All of these choices are correct.
topoisomerase
transfer of virulence from one cell to another
transformation
Agents that damage DNA can lead to mutations. t/f
true
All cells that have been examined show multiple pathways for repairing damaged DNA and for reversing errors that occur during replication. t/f
true
Although most mutations are harmful, some may be beneficial. t/f
true
Cancer cells generally have high levels of telomerase activity, which allows them to divide indefinitely without the chromosomes getting shorter and shorter. t/f
true
In addition to errors that occur during DNA replication, cells are constantly exposed to agents that can damage DNA, such as UV light, X-rays, and chemicals in the environment. t/f
true
Many DNA polymerases have 3'-to-5'exonuclease activity that allows "proofreading" and replacement of incorrect bases. t/f
true
A/T forms ___ H bonds
two
Eukaryotic organisms speed up the process of DNA replication by -using DNA gyrase to unravel the double helix rather than DNA helicase. -shortening the initiation phase. -producing several sliding clamp complexes which provide more binding sites for DNA pol III. -using multiple origins of replication on each chromosome.
using multiple origins of replication on each chromosome.
