bio 190a ch 9
the protein that separates DNA strands at the replication fork is
DNA helicase
which protein is needed to form a replication fork and keep it moving?
DNA helicase
Gaps in the sugar-phosphate backbone of DNA are closed by
DNA ligase.
How do DNA polymerase I and DNA Polymerase III differ?
DNA polymerase III synthesizes the majority of the DNA, while DNA polymerase I synthesizes DNA in the regions where the RNA primers were laid down on the lagging strand.Correct
The enzyme that travels along a template strand, assembling nucleotides into a growing DNA strand, is
DNA polymerase III.
the results of the Meselson and Stahl experiment are consistent only with what mechanism for DNA replication
semiconservative
Franklin determined that the structure of DNA was helical based on
x-ray diffraction analysis
Which of the following helps explain the remarkably high fidelity for DNA replication?
The hydrogen bonding between AT and CG pairs is more stable than between mismatched pairs DNA polymerase is unlikely to catalyze bond formation between adjacent nucleotides if a mismatched base pair is formed DNA polymerase can identify and repair mismatched nucleotides
the data of Chargaff suggested that DNA has similar amounts of A and T and of G and C. This conclusion was based on
a comparison of base composition of several different species
heterochromatin
describes the highly compacted regions of chromosomes during interphase. These radial loop domains are compacted even further
radial loop domains
involves interactions between the 30-nm fibers and proteins to form radial loop domains. One way that a radial loop is formed is by a category of proteins called SMC proteins. It stands for structural maintenance of chromosomes. An SMC protein forms a dimer that can wrap itself around two segments of DNA and thereby form a loop.
of the following statements, which is correct when considering the process of DNA replication?
new DNA molecules are composed of one strand from the old molecule and one new strand.
which of the following is the correct order for the progression of chromatin compaction seen in metaphase chromosomes?
nucleosomes, 30-nm fiber, radial loop domains, further compaction of radial loop domains
nucleotides have three components
phosphate group, pentose (five-carbon) sugar, and a nitrogen-containing base. The base and phosphate group are attached to the sugar molecule. The sugar Deoxyribose is found in DNA, the sugar Ribose is found in RNA.
The capsule present on Streptococcus pneumoniae Multiple choice question.
prevents the immune system from killing the organism
Match the proteins involved in DNA replication with their function.
helicase=causes DNA strand separation at the origin of replication topoisomerase=relieves coiling in DNA strands ahead of the replication fork single-strand binding protein=prevents the two DNA template strands from re-forming the double helix
A nucleosome consists of a core of
eight histone proteins: two each of H2A, H2B, H3, and H4
Considering the components of a nucleotide, what component is always different when comparing nucleotides in a DNA strand and in an RNA strand?
pentose sugar
The components of a nucleotide are
phosphate base sugar
The 5 prime end of a DNA strand has a _____ group, and the 3 prime end has a ____ group
phosphate ;OH
Newly-exposed, unreplicated DNA is protected by
single-strand binding protein.
what key features of DNA structure allow it to be replicated?
double-stranded and the AT/GC rule
structure of a nuclesome
A nucleosome is composed of double-stranded DNA wrapped around an octamer of histone proteins. A linker region connects two adjacent nucleosomes. Histone H1 is bound to the linker region, as are other proteins.
You have analyzed the base composition of the genetic material in a virus and found the following: 32% adenine, 17% thymine, 18% guanine, and 33% cytosine. From this analysis, which of the following is the most likely structure of the viral genome?
A. single-stranded DNA because A and T are not approximately equal, and G and C are not approximately equal.
DNA replication is very accurate because: 1. Hydrogen bonding according to the _____ rule is more stable than mismatched base pairs; 2. DNA polymerase is unlikely to catalyze bond formation if an incorrect base is added; and 3. DNA polymerase carries out _____
AT/GC; proofreading
Why did the injection of dead smooth bacteria not kill Griffith's mice? Multiple choice question.
Because dead bacteria are unable to cause disease
Of the following structural features of DNA, which has the highest level of complexity? Multiple choice question.
Genome
Why do you think it is necessary for the chromosomes to become highly compacted in preparation for cell division?
If chromosomes did not become compact, they could get tangled up with others during cell division, which would prevent the even segregation of chromosomes into the two daughter cells.
Which are enzymatic features of DNA polymerase?
It can only synthesize DNA in the 5' to 3' direction It is unable to begin DNA synthesis on a bare template strand
Beginning with the simplest level of structure, put each level of organization of genetic material in order.
Nucleotide DNA Gene Chromosome Genome
Watson and Crick, in collaboration with Witkins
Pauling built a ball-and-stick model to determine the structure of the alpha helix. Using the ball-and-stick approach, Watson and Crick and Wilkens set out to determine the structure of DNA. Watson and Crick proposed that the structure of DNA is a double helix in which the DNA strands are antiparallel and obey the AT/GC rule.
Before DNA polymerase can begin assembling DNA nucleotides to produce either the Okazaki fragments of the lagging strand or the continuous molecule of the leading strand, which must occur?
Primase constructs a short RNA primer.
Purines and Pyrimidines
Purines(double ring): Adenine and Guanine; found in both DNA and RNA Pyrimidines (single ring): Thymine and Cytosine and Uracil; Uracil is found only in RNA and Thymine is found only in DNA.
Short segments of RNA, called_______, are synthesized.
RNA primers
During DNA synthesis, the sites where the two template strands are unwound and new DNA is made are called what?
Replication forks
What statement best describes the results of the Avery, McLeod, and McCarty experiment that show DNA causes transformation in Streptococcus pneumoniae?
S. pneumoniae DNA degraded chemically does not cause transformation.
origin of replication in bacteria and eukaryotes
a bacterial chromosome is relatively small and usually circular and has a single origin of replication. Bidirectional replication starts at the origin of replication and proceeds until the new strands meet on the opposite side of the chromosome. Eukaryotes have larger chromosomes that are linear. They have multiple origins of replication, so the DNA can be replicated within a reasonable length of time.
What is attached to the 1' carbon atom and the 5' position?
a base is attached to the 1' carbon atom, and a phosphate group is attached at the 5' position.
For a molecule to serve as the genetic material, it must meet the following key criteria: information,
information replication transmission variation
Okazaki fragments are made during the synthesis of the ______ strand. They are connected together by _______.
lagging, DNA ligase
what would be the expected results for the Meselson and Stahl experiment after five generations? Note: Generation zero has all heavy DNA, and all subsequent generations use light nitrogen to make new DNA strands.
1/16 half-heavy, 15/16 light
according to Meselson and Stahl's procedure, what would be the predicted results after four generations according to the semiconservative model?
1/8 half-heavy and 7/8 light
A nucleosome is composed of
146 bp or 147bp of DNA an octamer of histone proteins
Arrange the following proteins in the proper order in which they participate in DNA replication.1 = Primase2 = Helicase3 = Single-strand binding proteins4 = DNA polymerase I
2, 3, 1, 4
A Meselson-Stahl experiment is performed on a bacterial culture. What percentage of DNA molecules is expected to be of intermediate density after three rounds of replication?
25%
The short RNA primers provide a free _____ for replication.
3' OH
Nucleosomes are organized into a more compact structure known as the ________ with the help of the histone protein ________. Multiple choice question.
30-nm fiber ; H1
Which of the following DNA sequences is complementary to 5' TAGAC 3'?
5' GTCTA 3'
DNA polymerase occasionally makes errors and adds an incorrect base. A new strand of DNA is being produced, and the template strand contains a G. Based on your knowledge of the structure of DNA, why is it more likely that DNA polymerase would accidently add a T to the new strand instead of a G or an A?
Because the structure of T and C are similar as they both have a single ring.
analyzed the base composition of DNA from different species and proposed that the amount of adenine in each case is equal to the amount of thymine.
Chargaff
which pyrimidine is found in both DNA and RNA?
Cytosine
leading and lagging strands in E. coli simplified
DNA primase makes one RNA primer in the leading strand and multiple RNA primers in the lagging strand. In E. coli, DNA polymerase III extends these primers with DNA, and DNA polymerase I removes the primers when they are no longer needed and fills in with DNA. DNA ligase connects adjacent Okazaki fragments in the lagging strand.
conservative mechanism
DNA replication produces 1 double helix with both parental strands and the other with 2 new daughter strands
semiconservative mechanism
DNA replication produces DNA molecules with 1 parental strand and 1 newly made daughter strand
Dispersive mechanism
DNA replication produces DNA strands in which segments of new DNA are interspersed with the parental DNA
Which are properties of the DNA double helix proposed by Watson and Crick? Multiple select question.
The DNA strands are antiparallel The DNA strands obey the AT/GC rule
In order to fit into cells, DNA must be
compacted
The difference between euchromatin and heterochromatin relates to the Multiple choice question.
compaction level of the molecule
The enzyme that synthesizes the RNA primers is an RNA polymerase called
primase.
DNA during the replication process
the two complementary strands of DNA separate and serve as template strands for the synthesis of daughter strands of DNA. After the double helix has separated, individual nucleotides have access to the template strands in a region called the replication fork. First, individual nucleotides hydrogen bond to the template strands according to the AT/GC rule. Next, a covalent bond is formed between the phosphate of one nucleotide and the sugar of the previous nucleotide. the end result is that two double helices are made that have the same base sequence as the original DNA molecule.
the difference in the synthesis of the leading and lagging strands is the result of which of the following?
the two template stands are antiparallel, and DNA polymerase makes DNA only in the 5' to 3' direction.
the DNA double helix has several distinguishing features
- DNA is a double-stranded structure with the sugar-phosphate backbone on the outside and the bases on the inside. it is a helical structure - the double helix is stabilized by hydrogen bonding between the bases in opposite strands to form base pairs - base pairing is specific. An adenine in one strand forms 2 hydrogen bonds with a thymine in the opposite strand, or a guanine forms three hydrogen bonds with a cytosine. this specificty is called the AT/GC rule. - the DNA strands are complementary to each other -one complete turn of the double helix is 3.4 nm in length and comprises about 10 base pairs - with regard to their 5' and 3' directionality, the two strands of a DNA double helix are antiparallel. -two grooves; major groove: occurs where the DNA backbones of the strands are farther apart. minor groove: is where they are closer together.
the key structural features of a DNA strand:
- Nucleotides are linked together by covalent bonds called phosphoester bonds between phosphorus and oxygen. The linkage in DNA strands is called a phosphodiester linkage, which has two phosphoester bonds. - The phosphates and sugar molecules form the backbone of a DNA or RNA strand, and the bases (thymine, adenine, cytosine, and guanine) project from the backbone. - A strand has a directionality based on the orientation of the sugar molecules within that strand. the direction of the strand is 5' to 3' when going from top to bottom. The 5' end of a DNA strand has a phosphate group, and the 3' end has an -OH group.
How is bacterial DNA replication similar to eukaryotic DNA replication? (Check all that apply.)
-Both bacterial and eukaryotic DNA replication occur in a bidirectional manner. -Both bacterial and eukaryotic DNA replication result in two DNA double helices that are both composed of one parental strand and one new strand. -Both bacterial and eukaryotic DNA replication use the same four nucleotides (A, C, G, and T)
DNA helicase, DNA topoisomerase, and single-strand binding proteins are responsible for fork formation and movement
-DNA helicase= At each fork, DNA helicase binds to one DNA strand and travels in the 5' to 3' direction. It uses energy from ATP to break hydrogen bonds between base pairs and thereby separates the DNA strands. This keeps the fork moving. -DNA topoisomerase= The action of DNA helicase can cause knots called supercoils to form just ahead of the replication fork. These knots are removed by another enzyme called DNA topoisomerase. -Single-strand binding proteins= After the two DNA strands have separated, they must remain that way so they can act as templates to make complementary daughter strands. The function of single-strand binding proteins is to coat both of the single strands of template DNA and prevent them from reforming a double helix.
two enzymes are needed to synthesize DNA strands during DNA replication
-DNA polymerase= is responsible for covalently linking nucleotides together to form DNA strands. The name indicates that this enzyme makes a polymer of DNA nucleotides -DNA primase= DNA polymerase is unable to begin DNA synthesis on a bare template strand. A different enzyme called DNA primase is required if the template strand is bare. DNA primase makes a complementary primer, which is actually a short segment of RNA, typically 10 to 12 nucleotides in length that starts, or primes, the process of DNA replication.
Suppose that, as in the Meselson-Stahl experiment, E. coli is grown for many generations in heavy nitrogen (15N) precursors, then shifted to light nitrogen (14N) precursors for 1 or 2 generations. Select the test tube that best corresponds to the positions that DNA would be expected to migrate in the following hypothetical situations. (Not all letters may be used, and some may be used more than once.)
-DNA replication is semiconservative, and the culture was grown in light media for 1 generation.= half heavy - DNA replication is conservative, and the culture was grown in light media for 1 generation.= Light and Heavy -DNA replication is semiconservative, and the culture was grown in light media for 2 generations= half-heavy and light -DNA replication is conservative, and the culture was grown in light media for 2 generations.= Light and Heavy -DNA replication is dispersive, and the culture was grown in light media for 1 generation.= Half-heavy - DNA replication is semiconservative, and the culture was grown in light media for 1 generation, then shifted back to heavy media for 1 more generation= Half-heavy and Heavy -Which tube represents the position expected if the bacteria were never shifted to light media at all?= Heavy
to determine the structure of DNA, Watson and Crick used
-the X-ray diffraction data of Franklin -the biochemical data of Chargaff -the ball-and stick model approach of Pauling
DNA polymerase has two additional enzymatic features that affect how DNA strands are made
1. DNA polymerase is able to covalently link nucleotides together from a primer, which is made by DNA primase 2. DNA polymerase can link nucleotides only in the 5' to 3' direction.
leading and lagging strands in E. coli steps
1. DNA primase makes RNA primers to begin the replication process 2. DNA polymerase iii makes DNA from the RNA primers. DNA primase hops back to the opening of the fork and makes a second RNA primer for the lagging strand. 3. DNA polymerase iii continues to elongate the leading strand. In the lagging strand, DNA polymerase iii synthesizes DNA from the second primer. DNA polymerase I removes the first primer and replaces it with DNA. 4. In the lagging strand, DNA ligase forms a covalent bond between the first and second Okazaki fragments. A third Okazaki fragment is made. The leading strand continues to elongate.
three factors explain such a remarkably high fidelity for DNA replication:
1. Hydrogen bonding between A and T or between G and C is more stable than hydrogen bonding between mismatched pairs of bases. 2. The active site of DNA polymerase is unlikely to catalyze bond formation between adjacent nucleotides if a mismatched base pair is formed. 3. DNA polymerase can identify a mismatched nucleotide and remove it from the daughter strand. This event is called proofreading, occurs when polymerase detects a mismatch and the reverses its direction and digests the linkages between nucleotides at the end of a newly made strand in the 3' to 5' direction. Once it passes the mismatched base and removes it, DNA polymerase then continues to synthesize DNA in the 5' to 3' direction.
genetic material must meet the following key criteria
1. Information- the genetic material must contain the information necessary to construct an entire organism 2. Replication- the genetic material must be accurately copied, a process known as DNA replication 3. transmission- after it is replicated, the genetic material can be passed from parent to offspring. it also must be passed from cell to cell during the process of cell division 4. variation- differences in the genetic material must account for the known variation within each species and among different species.
structural features of DNA at different levels of complexity:
1. Nucleotides= building blocks of DNA 2. Strand= DNA is formed by the covalent linkage of nucleotides in a linear manner 3. Double helix= two strands of DNA hydrogen bond with each other, two DNA strands that are twisted together to form a structure that resembles a spiral staircase, or helix 4. Chromosomes= in living cells, DNA is associated with an array of different proteins to form chromosomes. 5. Genome= is the complete complement of an organisms genetic material. for example, the genome of most bacteria is a single circular chromosome, whereas eukaryotic cells have DNA in their nucleus, mitochondria, and chloroplasts
the steps in eukaryotic chromosomal compaction leading to the metaphase chromosome
1. Wrapping of DNA around histone proteins to form nucleosomes 2. Formation of a 30-nm fiber via histone H1 and other DNA-binding proteins 3. Formation of radial loop domains 4. Further compaction of radial loops 5. Metaphase chromosome with 2 copies of the DNA
Rank the five levels of structural features of DNA. Start at the top with the most complex (or largest), and end at the bottom with the least complex (or smallest).
1. genome 2. chromosome 3. double helix 4. DNA strand 5. nucleotide
During what process are parental DNA strands used as templates for the synthesis of new DNA strands?
DNA replication
Chargaff also discovered critical information for the double helix
Chargaff analyzed the base composition of DNA that was isolated from many different species. His experiments consistently showed that the amount of adenine in each sample was similar to the amount of thymine, and the amount of cytosine was similar to the amount of guanine.
Match the description with the correct chromosomal structure.
Chromatin= protein-dna complex that makes up eukaryotic chromosomes Histone= individual proteins that DNA is wrapped around Nucleosome= 146-147 base pairs of DNA wrapped around 8 proteins 30-nm fiber= a zigzag of nucleosomes visible i the electron microscope Heterochromatin= highly compacted regions of chromosomes
A mutation results in the production of much less DNA ligase than normal. What would be a likely consequence?
DNA replication would occur, but replication of the lagging strand would take much longer than normal.
Avery, McLeod, and McCarty used established biochemical procedures to purify macromolecules from the type S streptococci. They found out that R bacteria can only be transformed by what type of purified macromolecule?
DNA
Avery, McLeod, and McCarty demonstrated that only purified
DNA can convert type R bacteria into type S.
The enzyme that catalyzes new DNA synthesis is
DNA polymerase.
The model organism used by Meselson and Stahl was ______. Multiple choice question.
Escherichia coli
histones
Eukaryotic DNA is first compacted by wrapping itself around a group of proteins called histones.
30-nm fiber
Nucleosome units are orgainzed into a more compact structure that is 30nm in diameter. Histone H1 and other proteins are important in the formation of the 30-nm fiber, which shortens the nucleosome structure another sevenfold. In one model for the 30-nm fiber, linker regions are relatively straight and the nucleosomes zigzag back and forth.
Which is involved in replicating the lagging strand?
Okazaki fragments primase DNA ligase
Griffith's bacterial transformation experiments indicated the existence of a genetic material
Step 1= when injected into a live mouse, the type S strain killed the mouse. The capsule made by a type S strain prevents the mouse's immune system from killing the bacterial cells. Following the death of the mouse, many type S bacteria were found in the mouses blood. Step 2= When type R bacteria were injected into a mouse, the mouse survived, and after several days, living bacteria were not found in the live mouse's blood because the mouse's immune system was able to destroy bacteria that had no capsule. Step 3= In a follow up to these results, Griffith also heat-killed the smooth bacteria and then injected them into a mouse. As expected, the mouse survived. Step 4= A surprising result occurred when Griffith mixed live type R bacteria with heat-killed type S bacteria and then injected them into a mouse- the mouse died. The blood from the dead mouse contained living type S bacteria! How did Griffith explain these results? He postulated that a substance from dead type S bacteria transformed the type R bacteria into type S bacteria. He called this process transformation, and he termed the unidentifiable material (DNA) responsible.
what are the four criteria that the genetic material must fulfill? What was Griffith's contribution to the study of DNA, and why was it important?
The genetic material must (1) contain the information necessary to construct an entire organism (2) be accurately copied (3) be transmitted from parent to offspring and from cell to cell during cell division in multicellular organisms and (4) contain variation that can account for the non-variation within each species and among different species. Griffith discovered something called the transformation principal and his experiments showed the existence of biochemical genetic information. in addition he showed that this genetic information can move from one individual to another of the same species. in his experiments Griffith took heat-killed type S bacteria and mix them with living type R bacteria and injected them into a live mouse which died after the injection. by themselves these two strains would not kill the mouse but when they were put together the genetic information from the heat-killed type S bacteria was transferred into the living type R bacteria thus transforming the type R bacteria into type S.
which strand, the leading or lagging strand, is made discontinuously in the direction opposite the movement of the replication fork?
The lagging strand is made discontinuously in the direction opposite to the movement of the replication fork.
Which of the following statements about DNA replication is TRUE?
The leading strand is synthesized continuously while the lagging strand is synthesized in a series of small fragments that are later connected
In the experiment of Avery, MacLeod, and McCarty, what was the purpose of using DNase, RNase, and protease if only the DNA extract caused transformation?
The researchers could not verify that the DNA extract was completely pure and did not have small amounts of contaminating molecules, such as proteins and RNA. The researchers were able to treat the extract with enzymes to remove proteins (using protease), RNA (using RNase), or DNA (using DNase). Removing the proteins or RNA did not alter the transformation of the type R to type S strains. Only the enzymatic removal of DNA disrupted the transformation, indicating that DNA is the genetic material.
synthesis of new DNA strands
The separation of DNA at the origin of replication produces two replication forks that move in opposite directions. New DNA strands are made near the opening of each fork. The leading strand is made continuously in the same direction the fork is moving. The lagging strand is made as small pieces (Okazaki fragments) in the opposite direction. These small pieces are then connected to each other to form a continuous lagging strand.
A principle of biology is that structure determines function discuss how the structure of DNA underlies different aspects of its function.
The structure of DNA provides a way for it to be replicated according to the AT/GC rule. in addition the sequences of bases within genes store information to make polypeptides with a defined amino acid sequence.
Avery, Macleod, McCarty used purification methods to reveal that DNA is the genetic material
They purified DNA from the type S bacteria and mixed it with type R bacteria, after allowing time for DNA uptake into the type R bacteria, they added an antibody that aggregated any nontransformed type R bacteria, which were then removed by centrifugation. The remaining bacteria were incubated overnight on petri plates. When the researchers mixed their S strain DNA extract with type R bacteria, some of the bacteria were converted to S bacteria, this result is consistent with the idea that DNA is the genetic material. When the DNA extracts were treated with RNase or protease, the type R bacteria were still converted into type S bacteria, indicating that contaminating RNA or protein in the extract was not acting as the genetic material. However, when the DNA extracts were treated with DNase, it lost the ability to convert type R bacteria into type S bacteria, this result is consistent with the idea that DNA is the genetic material.
Assuming DNA replication had been conservative, Meselson and Stahl would have observed what bands in the centrifuge tube after one round of replication? Multiple choice question.
Two bands: one heavy and one light
In the Avery, McLeod and McCarty experiment, which of the following mixtures would yield smooth colonies when plated?
Type R bacteria + type S DNA extract + RNase Type R bacteria + type S DNA extract Type R bacteria + type S DNA extract + protease
what is the difference between a phosphoester bond and a phosphodiester linkage?
a phosphoester bond is a single covalent bond between a phosphorus atom and an oxygen atom. A phosphodiester linkage involves two phosphester bonds. this linkage occurs along the backbone of DNA and RNA strands.
nucleosome
a repeating structural unit of chromatin is the nucleosome. Each nucleosome is composed of 146 or 147 base pairs of DNA wrapped around a core of eight histone proteins called histone octamer. Each octamer contains two molecules each of four types of histone proteins: H2A, H2B, H3, and H4
In DNA replication, the strands on the original molecule are used as ______ for the synthesis of new DNA strands.
templates
which of the following is NOT a property of DNA polymerase?
a. it cannot begin DNA synthesis on a bare template strand. b. it can elongate a DNA strand from a primer or pre-existing DNA strand c. it can synthesize DNA in the 3' to 5' direction d. it can synthesize DNA in the 5' to 3' direction Answer is C
Injection of which of the following in Griffith's experiments would cause the death of mice? Multiple select question.
dead smooth bacteria + live rough bacteria live smooth bacteria + live rough bacteria live smooth bacteria
Heterochromatin involves a tighter packing of loops as compared to
euchromatin
The pairing of nitrogenous bases in DNA is specific because
functional groups on each of the bases form hydrogen bonds with functional groups on only one other base.
In the work of Griffith, the mixture of heat-killed S strain bacteria and living R strain bacteria resulted in the death of the mouse. The correct interpretation of these results is that
genetic material was transferred from the heat-killed S strain to the R strain.
the conversion of euchromatin into heterochromatin involves
greater compaction of radial loop domains
During replication, the enzyme DNA _____ uses energy from ATP to separate the two strands. This generates additional coiling ahead of the replication fork that is alleviated by another enzyme called DNA ____
helicase; topoisomerase
During DNA replication, the newly made daughter strand is made according to the AT/GC rule. What critical function of DNA would be lost if the AT/GC rule was not followed during DNA replication?
in a DNA double helix, the two strands hydrogen-bond with each other according to the AT/GC rule. This provides the basis for DNA replication. In addition, as described in later chapters, hydrogen bonding between complementary bases is the basis for the transcription of RNA, which is needed for gene expression. it is the base sequence that allows DNA to store information. If the AT/GC rule was not followed, the ability to store information would be lost.
origin of replication
is a site within a chromosome that serves as a starting point for DNA replication. At the origin, the two DNA strands unwind. DNA replication proceeds outward from two replication forks, a process termed bidirectional replication.
______ and _____ performed an experiment that demonstrated the semiconservative mechanism of DNA replication. (Last names only please)
meselson and stahl
A metaphase chromosome is ______ a chromosome in a non-dividing cell. Multiple choice question.
more condensed than
During the replication of a DNA molecule
new base pairs must be formed according to Chargaff's rule.
Meselson and Stahl used two isotopes of the element ____ in their DNA replication experiments, so that the daughter strands could be distinguished from the parental strands.
nitrogen
The enzyme DNA_____ covalently links nucleotides to synthesize new DNA strands together during DNA replication.
polymerase
The enzyme DNA ______ is needed to begin DNA synthesis on a bare template strand. This enzyme makes a short segment of ____ called a primer that is complementary to a DNA sequence on the template strand.
primase; RNA
The proposed models for DNA replication included
semiconservative replication conservative replication dispersive replication
If a mouse died after infection with Streptococcus pneumoniae, Griffith would be able to find what type of bacteria in its blood? Multiple choice question.
smooth live
The DNA strands that can be copied to produce new DNA strands are called the
template strands.
Franklin
the diffraction pattern of DNA fibers produced by Franklin suggested a helical structure with a diameter that is relatively uniform and too wide to be a single-stranded helix. X-ray diffraction was the key experimental tool that led to the discovery of the DNA double helix.
euchromatin
the less condensed regions which is the form of chromatin in which the 30-nm fiber forms radial loop domains. In nondividing cells, most chromosomal regions are euchromatic, and these are the regions where genes are usually located. By comparison, the centromeric and telomeric regions are often heterochromatic and may not contain genes.
the terms 5' and 3' refer to the directionality of a DNA strand based on
the orientation of sugar molecules in the backbone
DNA replication
the original DNA strands are used as templates for the synthesis of new DNA strands.
DNA replication according to the AT/GC rule continued..
the synthesis of one newly made strand (the leading strand, on the left side) occurs in the direction toward the replication fork, whereas the synthesis of the other newly made strand (the lagging strand, o the right side) occurs in small segments away from the fork. DNA replication produces two copies of DNA with the same sequence of bases as the original DNA molecule.
The semiconservative mechanism of DNA replication produces
two molecules each with a parental strand and a daughter strand