mastering genetics ch 10 DNA REPLICATION
In the Meselson-Stahl experiment, which mode of replication was eliminated based on data derived after one generation of replication? conservative semiconservative dispersive none of the modes
conservative The conservative replication theory says that parental strands reanneal with parental strands and daughter strands reanneal with daughter strands after DNA replication. This experiment showed that this was not the case.
Which model of DNA could be eliminated after the results of the first round of DNA replication? conservative model dispersive model semiconservative model both the dispersive and semiconservative models
conservative model
4. After replication is complete, the strand of new DNA, called_____ _______, is complementary to the parental strand.
daughter DNA
Okazaki fragments are short DNA fragments synthesized in a _______________ manner.
discontinuous
The discovery of Okazaki fragments suggested that DNA synthesis is __________. continuous semiconservative discontinuous conservative
discontinuous DNA must be synthesized on both strands of the double helix at the same time. However, one strand runs in a 5' to 3' direction, and the other runs in the 3' to 5' direction. For replication to occur on both strands in the same direction simultaneously, one strand must be made in a discontinuous fashion (in short pieces called Okazaki fragments) and reannealed later.
Okazaki fragments are short DNA fragments synthesized in a ______________ manner
discontinuous manner
After observing the results of one round of replication, the scientists obtained results from a second round. The purpose of one additional round of replication was to _______. confirm that replication is conservative distinguish between conservative and dispersive replication distinguish between semi-conservative and dispersive replication distinguish between conservative and semi-conservative replication
distinguish between semi-conservative and dispersive replication After one round of replication, the results of these two possibilities are indistinguishable. A second round was required to distinguish between these two possibilities.
Which enzyme catalyzes the addition of nucleotides to a growing DNA chain? Primase DNA polymerase Helicase Telomerase
dna polymerase DNA polymerase catalyzes the addition of nucleotides to a growing DNA chain.
The data obtained from the Meselson-Stahl experiment after one generation of replication eliminated the dispersive model of DNA replication. t/f
false The data obtained from the Meselson-Stahl experiment after one generation was consistent with both the semiconservative and the dispersive model of DNA replication. The conservative model of DNA replication was eliminated because it predicted that there would be two bands representing the original DNA at one density and the newly replicated DNA at a different density.
All EXCEPT which of the following are related to telomeres? telomerase enzyme found in eukaryotes and prokaryotes links to the aging process short tandem repeats located at the ends of telomeres
found in eukaryotes and prokaryotes Telomeres are found in eukaryotes but not prokaryotes.
Which enzyme in E. coli is responsible for relieving the tension ahead of the fork that results when the DNA is unwound to form the replication bubble or eye? DNase helicase gyrase primase
gyrase Gyrase relieves the tension by forming negative supercoils in a reaction that requires energy from the hydrolysis of ATP
Proteins which require the energy normally supplied by the hydrolysis of ATP to break hydrogen bonds and denature the double helix, are called _______ What are some examples? .
helicases DNAa DNAb DNAc
Which term describes a genetic exchange between two DNA molecules with substantial DNA sequence homology? somatic recombination illegitimate recombination tetrad exchange homologous recombination
homologous recombination General, or homologous, recombination requires a great deal of DNA sequence homology for the two molecules to recombine. Return to Assignment
3. Okazaki fragments appear on the ________ strand during DNA replication.
lagging
The newly synthesized DNA strand is called ________ The opposite strand is called _____ and also undergoes discontinuous DNA synthesis
leading lagging
5. The new DNA strand that grows continuously in the 5' to 3' direction is called the ____ _____
leading strand
CLASSES OF CELLULAR RNA carries genetic information from DNA of the gene to the ribosome
mRNA
________ thus specifies amino acid sequence by ACTING THROUGH tRNA
mRNA mRNA cannot directily bind to amino acids, but instead interacts with tRNA (transfer-RNA), which has a binding site for an amino acid, and a sequence of three nucleotides on another side (anticodon).
____ _______ are the short sections of DNA that are synthesized on the lagging strand of the replicating DNA.
okazaki fragments
___ _____ are short sequences of DNA nucleotides which are synthesized discontinuously and later linked together by the enzyme DNA ligase to create the lagging strand during DNA replication.
okazaki strands
Semiconservate replication uses each strand of the parent double helix as a template, and each newly replicated double helix includes one ____ and one _____ strand of DNA
old + new
If the dispersive model of DNA replication were correct, how many bands would have been observed by Meselson and Stahl after two rounds of replication? One Two Three Four
one
A single point of origin along the circular chromosome of most bacteria and viruses at which DNA synthesis is initiated is called _____
oriC
consists of 245 nucleotide pairs characterized by repeating sequences of 9 and 13 bases
oriC
DNA ligase then forms ___________ bonds between DNA Okazaki fragments.
phosphodiester
Synthesis of the RNA is directed by a form of RNA polymerase called ____
primase
Degree to which an enzyme is able to catalyze consecutive reactions before it dissociates from the substrate
processivity
CLASSES OF CELLULAR RNA largest in size and constitutes 80% of all RNA in a cell. Acts as workbenches during translation.
rRNA
3. During DNA replication, an open Y shaped section of DNA, in which a DNA polymerase can replicate DNA, is called a ____ ______
replication fork
What term accurately describes the replications of DNA in vivo?
semi-discontinuous/semi-conservative
Which structure within the DNA polymerase III holoenzyme is responsible for maintaining the binding of the core enzyme to the template during polymerization of nucleotides? θ subunit ε subunit α subunit sliding DNA clamp
sliding DNA clamp he sliding DNA clamp functions alongside the core enzyme and acts as the processivity factor.
CLASSES OF CELLULAR RNA Carries amino acids to ribosomes
tRNA
The enzymatic function of the ____ ____ _____ loader is dependent on energy generated by the hydrolysis of ATP. The ___ ____ ____ links to the core enzyme and is shaped like a donuts, whereby is can open and shut to encircle the unreplicated DNA helix. This leads the way during synthesis maintaining the binding of the core enzyme to the template during polymerization of nucleotide.
the DNA clamp
All EXCEPT which of the following are differences between eukaryotic and prokaryotic DNA replication? the ability to form a replication fork the number of replication origins the type and number of polymerases involved in DNA synthesis the rate of DNA synthesis
the ability to form a replication fork Both prokaryotes and eukaryotes form replication forks during DNA replication.
All of the following are differences between eukaryotic and prokaryotic DNA replication EXCEPT __________. the rate of DNA synthesis the ability to form a replication fork the number of replication origins the type and number of polymerases involved in DNA synthesis
the ability to form a replication fork Both prokaryotes and eukaryotes form replication forks during DNA replication.
The results of the Meselson-Stahl experiments relied on all of the following except _______. a means of distinguishing among the distribution patterns of newly synthesized and parent molecule DNA possible that a heavy isotope of nitrogen could be incorporated into replicating DNA molecules a cesium chloride gradient the fact that DNA is the genetic material
the fact that DNA is the genetic material
Taylor, Woods and Hughes demonstrated semiconservative replicatoin in Eukaryotas using ______________________ as the source of dividing cells.
the root tips of the broad bean
Where does DNA polymerase III add nucleotides?
to the 3' end of the RNA primer
___________ the first step in gene expression and involves copying a genes DNA sequence to make an RNA molecule. It does so using RNAS polymerase which link nucleotide to form an RNA strand
transcription
Is responsible for removing the primer and filling the gaps that occur during DNA synthesis A. DNA POLYMERASE 1 B. DNA POLYMERASE 2 C. DNA POLYMERASE 3
A. DNA POLYMERASE 1
__ ______ IS BELIEVED TO BE RESPONSIBLE FOR REMOVING THE PRIMER (DURING EXCISING THE INCORRECT NUCLEOTIDE) AND AS WELL AS FOR SYNTHESIS THAT FILLS GAPS PRODUCED AFTER THIS REMOVAL. A. polymerase 1 B. polymerase 2 C. polymerase 3
A. POLYMERASE 1
In bacteria, DNA replication begins at the origin of replication and is ________ A. bidirectional B. unidirectional
A. bidrectional
All EXCEPT which of the following are required for the synthesis of DNA in vitro by DNA polymerase? primer template deoxynucleoside triphosphates ATP
ATP TP is not required because the energy needed to catalyze the polymerization is obtained when the nucleotide triphosphates are hydrolyzed to nucleotide monophosphates and inorganic pyrophosphate.
a photographic emulsion is placed over a hisological preparation containing cellular material and the preparation is stored in the dark, radioisotopes emits energy upon development and the emulsion turns black at emission and you may be able to pinpoint the location of the radioisotope
Autoradiography
___________ _ is encoded by a gene whose transcription is activated by disruption of DNA synthesis at the replication fork A. polymerase 1 B. polymerase 2 C. polymerase 3
B. polyermase 2
Which primer synthesize so that polymerization can commence under the direction of DNA polymerase 3? A. DNA B. RNA
B. rna
_____ ____ is the enzyme responsible for the 5' - > 3' polymerization essential to in vivo replication A. polymerase 1 B. polymerase 2 C. polymerase 3
C. polymerase 3
____ _____ makes either single or double stranded "cuts" and also catalyzes localized movements that have the effect of "undoing" the twists and knots created during super coiling. This is powered by the released energy of ATP hydrolysis
DNA GYRASE
Which one of the following proteins and enzymes does NOT function at the origin of replication in E. coli? helicase DnaA, DnaB, and DnaC proteins SSBPs DNA ligase
DNA LIGASE DNA ligase catalyzes the last reaction in DNA replication on the lagging strand; it seals the nick and joins the Okazaki fragments. This reaction does not occur at the origin of replication.
___ ____ proofreads the newly built strands in progress, checking that the nexly added nucleotide is in fact complementary
DNA POLYMERASE
_____ ____ a key to replication enzyme, travels along the 5' - > 3' adding free nucleotides.
DNA POLYMERASE
_____ ______ is a central process in biochemistry and must be done with the highest precision. If a mistake is made in the replication of DNA, the error will propagate into future generations. An error that occurs during replication is called a mutation.
DNA REPLICATION
Which enzyme in E. coli is responsible for relieving the tension ahead of the fork that results when the DNA unwinds to form the replication "bubble" or "eye"? helicase DNA gyrase DNase primase
DNA gyrase Gyrase relieves the tension by forming negative supercoils in a reaction that requires energy from the hydrolysis of ATP.
Discontinous synthesis of DNA requires enzymes that both remove the RNA primer and unite the Okazaki fragments into the lagging strand, this is called ___________ _________-
DNA ligase
2. The enzyme that can replicate DNA is called _______ ________.
DNA polymerase
____ __________ I removes the RNA primers and fills in the gaps with DNA nucleotides.
DNA polymerase
Which enzyme catalyzes the addition of nucleotides to a growing DNA chain? primase helicase DNA gyrase DNA polymerase
DNA polymerase DNA polymerase catalyzes the addition of nucleotides to a growing DNA chain.
Which DNA polymerase is responsible for the removal of the RNA primers at the origin and at the 5' ends of the Okazaki fragments in E. coli? DNA polymerase II primase DNA polymerase I DNA polymerase IV
DNA polymerase I The 5' to 3' exonuclease activity of DNA polymerase I is responsible for RNA primer removal.
Which DNA polymerase is mainly responsible for genome replication in E. coli? DNA polymerase III DNA polymerase II DNA polymerase α DNA polymerase I
DNA polymerase III DNA polymerase III is responsible for the synthesis of the bulk of the DNA in E. coli.
which of the following statements about DNA replication is true? DNA synthesis is discontinuous on the leading strand. DNA synthesis is conservative on the leading strand and semiconservative on the lagging strand. The two replication forks move in the same direction. DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand.
DNA synthesis is continuous on the leading strand and discontinuous on the lagging strand. This statement correctly describes the conditions of DNA replication.
This particular protein is in charge of unwinding the the helix
DNAa
______ and ______ proteins further open and destabilize the helix
DNAb and DNAc
What is the difference between a disassociative enzyme and a processive enzyme?
Diassociative -> enzymes does reaction in parts processive -> enzyme keeps catalyzing until reaction is complete and then falls off
Bacteria are dependent on telomerase to complete synthesis of their chromosome ends T/F
FALSE
Primase does need a free 3' to begin synthesis T/F
FALSE
DNA Polymerase 1,2,3 can INITIATE DNA synthesis on a template t/f
FALSE they can only ELONGATE IT
Which have stronger bonds? A-T? G-C?
G-C have 3 hydrogen bonds compared to A-T (2) more hydrogen bonds = stronger
The DNA is wound around a histone protein care to form a _______. This gives a 5 --> 9 reduction in length
Nucleosome
Which of the following would result from a third round of replication using the methods of Meselson and Stahl? One light band and one intermediate band One heavy band One heavy band, one light band, and one intermediate band One light band
One light band and one intermediate band Of the molecules generated in the third round, 75% are completely light, 25% are intermediate
For the 4 nucleotides which ones are Purine? Which ones are Pyrimidines
Purines A and G Pyrimidines C, T, and U
What are the main difference between RNA and DNA makeup?
RNA = single strand the sugar in RNA is Ribose Does not contain thymine contains URACIL
RNA contains ____ as its sugar DNA contains _____ as its sugar
RNA = ribose DNA = deoxyribose
Once a small portion of the helix is unwound, what is needed to initiate synthesis?
RNA is needed as the primer (polymerase 3 needs a primer to start)
Which enzyme or enzymatic activity is NOT involved in resolution of the Okazaki fragments in E. coli? 5′ to 3′ exonuclease activity of DNA polymerase I RNA ligase 5′ to 3′ polymerase activity of DNA polymerase I DNA ligase
RNA ligase Correct. There is no RNA to ligate once the RNA primer is removed from the DNA fragments.
RNA primers are formed by ____________ ________ and serve as an initiation point for DNA synthesis on the template.
RNA primase
This technique was used in the Meselon-Stahl experiment. Sample are forced by centrifugation through a density gradient of a heavy metal salt such as cesium chloride. Molecules of DNA will then reach equilibrium when their density equals the density of the gradient medium, in this case 15N-DNA will reach the point at a position close to the bottom of the tube than will 14N-DNA
Sedimentation equilibrium centrifugation
Method of DNA replication in which parental strands separate, act as templates, and produce molecules of DNA with one parental DNA strand and one new DNA strand
Semi Conservative
Which of the following statements about DNA replication is true? DNA polymerase adds dNTP monomers in the 3′-5′ direction. Single‑strand binding proteins stabilize the open conformation of the unwound DNA. DNA gyrase unwinds the DNA double helix. Okazaki fragments are DNA fragments synthesized on the leading strand.
Single‑strand binding proteins stabilize the open conformation of the unwound DNA. Once helicase unwinds the double helix, single‑strand binding proteins bind to the open DNA and prevent it from winding together again.
Structures located at the ends of eukaryotic chromosomes are called ________. recessive mutations telomerases permissive mutations telomeres centromeres
TELOMERES
All DNA polymerase enzymes have the potential to polymerize in one direction and then pause and reverse direction T/F
TRUE
DNA strand replication begins with an RNA primer. T/F
TRUE
when DNA proteins are be assembled, the mRNA sequence is IDENTICAL to the DNA template T/F
TRUE
What gives a DNA molecule its direction?
The 5-phosphate` group of the one nucleotide joins to the 3' OH group of the next nucleotide (VERY STRONG BOND)
Why is an RNA primer considered essential for DNA synthesis by DNA polymerase III? There is no particular reason; that is simply what has been observed. The enzyme requires a free 3′-OH group to initiate synthesis. The enzyme requires a free 3′-PO4 group to initiate synthesis. The enzyme requires a free 5′-PO4 group to initiate synthesis.
The enzyme requires a free 3′-OH group to initiate synthesis. Polymerase III requires a free 3'-OH group to begin synthesis of DNA. An RNA primer provides a 3' hydroxyl group from which the DNA polymerase can initiate synthesis.
A _________ contains the nitrogenous base and the pentose sugar
a nucleoside
In the Meseleson-Stahl experiment, which of the 2 modes of replication could be ruled out after one around of replication? After two rounds?
after rd. 1 the conservative can be ruled out due to the 14N DNA is of intermediate density, just as it is in the semiconservative model, HOWEVER, rd.2 showed the density of DNA is between the intermediate and the "light" density and therefor ruled out
The presence of a single origin for DNA synthesis is a characteristic of ____ They have only ____ circular chromosome
bacteria 1
Which terms accurately reflect the nature of replication of the chromosome in E. Coli?
bidirectional and fixed point of initiation
Before DNA proteins can be assembled, what two processes must occur first?
1. TRANSCRIPTION 2. TRANSLATION
CLASSES OF CELLULAR RNA ____ are the templates for protein synthesis ______ carry amino acids for protein synthesis ______ are components of ribosomes for protein synthesis
1. mRNA 2. tRNA 3. rRNA
What 3 items does DNA consist of?
1. nitrogenous base 2. pentose sugar 3. a phosphate group
How does DNA cells Divide?
1. the weak H bonds between the strands break, exposing the nucleotideS 2. the unpaired base will attract a free nucleotide that has the COMPLEMENTARY BASE 3. enzymes assist in unwinding, holding strands apart, gluing pieces back together etc. 4. DNA POLYMERASE travels along the DNA strand addding free nucleotides to the 3' end of the new strand (5'->3') 5. built
In the DNA double helix, the A-T pair form __ hydrogen bonds whereas the G-C pair form _____ hydrogen bonds
2 3
During chain elongation, as the nucleotide is added, what is cleaved off?
2 terminal phosphates
Which activity of E. coli DNA polymerase I is responsible for proofreading the newly synthesized DNA? 5′ to 3′ exonuclease 5′ to 3′ polymerase 3′ to 5′ exonuclease 3′ to 5′ endonuclease
3′ to 5′ exonuclease If the wrong nucleotide is inserted, normal base pairing will not be observed, and the base in error will be removed from the newly synthesized strand before subsequent nucleotides are added.
DNA Polymerase can only copy strands in what direction?
5 prime -> 3 prime
chain elongation only occurs in the ___ __ __ ___-- direction
5->3 direction
The overall rate of eukaryotic DNA replication is essentially the same as it is in prokaryotes, even though eukaryotic genomes are hundreds to thousands of times bigger than their prokaryotic counterparts. Which of the following statements could account for this observation? The Okazaki fragments in eukaryotes are much longer. DNA replication in eukaryotes occurs during a defined phase in the cell cycle. There are more replication origins in eukaryotes. The DNA polymerases in eukaryotes are much larger.
There are more replication origins in eukaryotes. There are many more origins of replication, which define a replicon, allowing more DNA to be synthesized at any one time.
Which of the following statements is TRUE regarding Okazaki fragments? They are synthesized by ligase. They are short fragments of RNA joined by DNA ligase. They add nucleotides to the elongating DNA. They are short fragments of DNA joined by DNA ligase.
They are short fragments of DNA joined by DNA ligase. Okazaki fragments are short sequences synthesized in the lagging strand because DNA polymerase can synthesize only from 5′ to 3′ and the template DNA strands are antiparallel.
Which of the following statements is true regarding Okazaki fragments They are short fragments of DNA synthesized from RNA primers on the lagging strand. They are short fragments of RNA on the leading strand. They are synthesized by ligase. They add nucleotides to the elongating DNA.
They are short fragments of DNA synthesized from RNA primers on the lagging strand. Okazaki fragments are short sequences synthesized in the lagging strand because DNA polymerase can synthesize only from 5' to 3' and the template DNA strands are antiparallel.
