chapter 13
How do we describe transformation in bacteria?
assimilation of external DNA into a cell
In order to insert a human gene into a plasmid, both must _____
be cut by the same restriction enzyme; Doing so will result in the formation of complementary sticky ends.
Which of these is a vitamin A precursor?
beta-carotene; The body can convert beta-carotene into vitamin A.
Which of these is a symptom of vitamin A deficiency?
blindness; Chronic vitamin A deficiency can lead to blindness.
The cells examined from the 2,400 people in this study were from ______.
blood
How does a bacterial cell protect its own DNA from restriction enzymes?
by adding methyl groups to adenines and cytosines
For the first time, the U.S. Food and Drug Administration is considering whether to allow the sale of _____.
food from a genetically altered animal
What is the function of topoisomerase?
relieving strain in the DNA ahead of the replication fork
Polytene chromosomes of Drosophila salivary glands each consist of multiple identical DNA strands that are aligned in parallel arrays. How could these arise?
replication without separation
The transfer of antibiotic-resistant genes from genetically engineered bacteria to disease-causing bacteria _____.
seems unlikely; It seems unlikely to occur and there is no evidence that it has occurred.
The modified salmon were created by _____.
adding genetic material from a Pacific salmon and an eel-like fish
Will grow in both media
*Recombinant plasmid with vgp gene *Nonrecombiant plasmid *Recombinant plasmid but no vgp gene
The sticky end of the DNA restriction fragment shown here will pair with a DNA restriction fragment with the sticky end _____. TGCA
-ACGT The matching of sticky ends follows the rules of specific base pairing.
How many DNA molecules would there be after four rounds of PCR if the initial reaction mixture contained two molecules?
32; Thirty-two DNA molecules are produced if two molecules are doubled four times.
At a specific area of a chromosome, the following sequence of nucleotides is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T (T) of the template. Which of the following represents the primer sequence?
5' A C G U U A G G 3'
An Okazaki fragment has which of the following arrangements?
5' RNA nucleotides, DNA nucleotides 3'
Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
8%
Why is it so important to be able to amplify DNA fragments when studying genes?
A gene may represent only a millionth of the cell's DNA.
What is the polymerase chain reaction (PCR)?
A method to amplify a fragment of DNA.; PCR is an in vitro DNA synthesis reaction that produces many copies of a single DNA fragment.
What is genetic cloning?
A method to produce many copies of a gene;Genetic cloning is the process by which many identical copies of a gene are produced.
In gel electrophoresis DNA molecules migrate from _____ to _____ ends of the gel.
An electrical current is generated across the gel, and DNA molecules migrate from the negative end toward the positive end.
During which step in the PCR cycle do primers form bonds with a single-stranded template?
Annealing.; Primers form hydrogen bonds with the single-stranded DNA template during the annealing step.
Rank the primers in the order they were produced. If two primers were produced at the same time, overlap them.
As soon as the replication bubble opens and the replication machinery is assembled at the two replication forks, the two primers for the leading strands (primers a and h) are produced. The production of the first primers on the lagging strands (those closest to the origin of replication, b and g) is delayed slightly because the replication forks must open up further to expose the template DNA for the lagging strands. After completion of the first segments of the lagging strands, additional template DNA must be exposed before the second primers (c and f) can be produced. And after completion of the second segments, additional template DNA must be exposed before the third primers (d and e) can be produced. In summary, because of the way the replication bubble expands, the lagging strand primers near the origin of replication were produced before the primers near the replication forks.
As DNA replication continues and the replication bubble expands, the parental double helix is unwound and separated into its two component strands. This unwinding and separating of the DNA requires three different types of proteins: helicase, topoisomerase, and single-strand binding proteins.
At each replication fork, helicase moves along the parental DNA, separating the two strands by breaking the hydrogen bonds between the base pairs. (This makes the two parental DNA strands available to the DNA polymerases for replication.) As soon as the base pairs separate at the replication fork, single-strand binding proteins attach to the separated strands and prevent the parental strands from rejoining. As helicase separates the two parental strands, the parental DNA ahead of the replication fork becomes more tightly coiled. To relieve strain ahead of the replication fork, topoisomerase breaks a covalent bond in the sugar-phosphate backbone of one of the two parental strands. Breaking this bond allows the DNA to swivel around the corresponding bond in the other strand and relieves the strain caused by the unwinding of the DNA at the helicase.
Which one restriction enzyme satisfies all three of the requirements listed above?
BamHI only; BamHI cuts the plasmid outside the ampR gene, leaving the gene intact and functional, which is important for the next step in the cloning procedure. Once BamHI opens the plasmid, the sticky ends it produces in the plasmid can base-pair with those on BamHI human DNA fragments. If DNA ligase is then added, it will covalently join the sugar-phosphate backbones of the plasmid and the fragments, producing recombinant plasmids. Note that human DNA contains many BamHI restriction sites in addition to the two shown in Part A. Therefore, only a small fraction of the recombinant plasmids will have the vgp gene, like the plasmid shown above. Most of the recombinant plasmids will have a fragment of human DNA that does not contain the vgp gene, and would not be of interest to the scientists.
Which enzyme(s) would cut the plasmid without disrupting the function of the ampR gene?
BamHI, EcoRI, and HaeIII
Which enzyme(s) would produce sticky ends when cutting both the human DNA and the plasmid?
BamHI, EcoRI, and HindIII
Which enzyme(s) would cut the human DNA shown in Part A on both sides of the vgp gene, but not inside the gene?
BamHI, HaeIII, and HindIII
Drag each phrase to the appropriate bin depending on whether it describes the synthesis of the leading strand, the synthesis of the lagging strand, or the synthesis of both strands.
Because DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand and because the two parental DNA strands are antiparallel, synthesis of the leading strand differs from synthesis of the lagging strand. The leading strand is made continuously from a single RNA primer located at the origin of replication. DNA pol III adds nucleotides to the 3' end of the leading strand so that it elongates toward the replication fork. In contrast, the lagging strand is made in segments, each with its own RNA primer. DNA pol III adds nucleotides to the 3' end of the lagging strand so that it elongates away from the replication fork. In the image below, you can see that on one side of the origin of replication, a new strand is synthesized as the leading strand, and on the other side of the origin of replication, that same new strand is synthesized as the lagging strand. The leading and lagging strands built on the same template strand will eventually be joined, forming a continuous daughter strand.
cloning
Cloning occurs with the replication of a recombinant plasmid
What are chromosomes made of?
DNA and proteins; Long DNA molecules are associated with proteins that allow DNA to coil and pack
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
What enzyme forms covalent bonds between restriction fragments?
DNA ligase; DNA ligase catalyzes the formation of covalent bonds between restriction fragments.
I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?
DNA polymerase I
Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
DNA polymerase III
Drag the arrows onto the diagram below to indicate the direction that DNA polymerase III moves along the parental (template) DNA strands at each of the two replication forks. Arrows can be used once, more than once, or not at all.
DNA polymerase III can only add nucleotides to the 3' end of a new DNA strand. Because the two parental DNA strands of a double helix are antiparallel (go from 3' to 5' in opposite directions), the direction that DNA pol III moves on each strand emerging from a single replication fork must also be opposite. For example, in the replication fork on the left, the new strand on top is being synthesized from 5' to 3', and therefore DNA pol III moves away from the replication fork. Similarly, the new strand on the bottom of that same replication fork is being synthesized from 5' to 3'. But because the bottom parental strand is running in the opposite direction of the top parental strand, DNA pol III moves toward the replication fork. In summary, at a single replication fork, one strand is synthesized away from the replication fork, and one strand is synthesized toward the replication fork. When you look at both replication forks, note that a single new strand is built in the same direction on both sides of the replication bubble.
The radioactive isotope 32P labels the T2 phage's _____.
DNA, The T2 phage consists of a protein coat and DNA. It is the DNA that contains P.
After mixing a heat-killed, phosphorescent (light-emitting) strain of bacteria with a living, nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observation(s) would provide the best evidence that the ability to phosphoresce is a heritable trait?
Descendants of the living cells are also phosphorescent.
DNA replication is said to be semiconservative. What does this mean?
Each new double helix consists of one old and one new strand. This is the meaning of the term "semiconservative."
Which of the following investigators was (were) responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.
Erwin Chargaff
During which step in the PCR cycle are nucleotides used?
Extension.; Nucleotides are used to synthesize the complementary strand to the DNA template during the extension step.
True or false? The use of growth hormone isolated from cadavers was banned mainly because there were not enough cadavers to supply the hormone.
False: The use of growth hormone isolated from cadavers was banned mainly because the isolated hormone was potentially contaminated with prion proteins.
True or false? The Taq enzyme is a type of DNA polymerase that allows researchers to separate the DNA strands during the annealing step of the PCR cycle without destroying the polymerase.
False; Taq polymerase is derived from a species of bacteria living in hot springs, which makes it stable at the high temperature required for the denaturation step of PCR
Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?
Franklin, Rosalind Franklin conducted these X-ray diffraction studies of DNA.
Which of the following is a concern expressed by opponents of the use of genetically modified (GM) food crops?
GM food crops might pass their new genes to close relatives in nearby wild areas. The protein products of transgenes in GM food crops might lead to allergic reactions in human consumers. Read about the safety and ethical questions raised by DNA technology
Who demonstrated that DNA is the genetic material of the T2 phage?
Hershey and Chase did a series of classic experiments demonstrating that DNA is the genetic material of the T2 phage.
Which enzyme(s) will produce a DNA fragment that contains the entire vgp gene (shown in red) and has "sticky ends"?
HindIII BamHI Cloning the vgp gene requires an enzyme that has restriction sites on both sides of that gene but not within the gene. Two enzymes, HindIII and BamHI, satisfy that requirement, while also producing DNA fragments that have sticky ends. Sticky ends make it possible for the fragments to combine with the DNA of a cloning vector, such as a plasmid.
Which of the following statements is true of histones?
Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together.
Why do histones bind tightly to DNA?
Histones are positively charged, and DNA is negatively charged.
What is the most logical sequence of steps for splicing foreign DNA into a plasmid and inserting the plasmid into a bacterium? I. Transform bacteria with a recombinant DNA molecule. II. Cut the plasmid DNA using restriction enzymes. III. Extract plasmid DNA from bacterial cells. IV. Hydrogen-bond the plasmid DNA to nonplasmid DNA fragments. V. Use ligase to seal plasmid DNA to nonplasmid DNA.
III, II, IV, V, I
In which image will adenine (A) be the next nucleotide to be added to the primer?
In the example above, DNA pol III would add an adenine nucleotide to the 3' end of the primer, where the template strand has thymine as the next available base. You can tell which end is the 3' end by the presence of a hydroxyl (-OH) group. The structure of DNA polymerase III is such that it can only add new nucleotides to the 3' end of a primer or growing DNA strand (as shown here). This is because the phosphate group at the 5' end of the new strand and the 3' -OH group on the nucleoside triphosphate will not both fit in the active site of the polymerase.
Which of the following statements describes the eukaryotic chromosome?
It consists of a single linear molecule of double-stranded DNA plus proteins.
Why is golden rice pale yellow in color?
It is rich in beta-carotene.; Beta-carotene confers a yellow color on the rice.
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
It joins Okazaki fragments together.
Which of the following statements best describes the function of reverse transcriptase?
It makes complementary DNA (cDNA) from mRNA.; The function of reverse transcriptase is similar to the reverse of transcription; it makes a single strand of complementary DNA (cDNA) from mRNA.
What is the function of helicase in DNA replication?
It untwists the double helix and separates the two DNA strands. By pulling apart and untwisting the DNA strands, helicase makes them available for replication.
What defect causes pituitary dwarfism?
Lack of growth hormone; Affected individuals produce little or no growth hormone.
The researchers used strands of DNA located at the ends of chromosomes (called telomeres) to classify the cells they studied. What assumption did they make about telomeres?
Longer telomeres indicate younger cells.
Which of the following steps would be performed last when screening a cDNA library?
Match the region of radioactivity on the filter with the corresponding plate.
In his transformation experiments, what did Griffith observe?
Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.
Will only grow in medium without ampicillin
No plasmid; Only bacteria that were transformed (picked up a plasmid) can grow in a medium containing ampicillin. Each transformed bacterium reproduces, forming a clone of cells. The complete set of clones is called a plasmid library. Some clones in the library have nonrecombinant plasmids, some have recombinant plasmids without the vgp gene, and a small fraction have recombinant plasmids with the vgp gene.
In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin. Which of the following would you expect as a result of this mutation?
No replication fork will be formed.
Replication in prokaryotes differs from replication in eukaryotes for which of the following reasons?
Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many
How can large quantities of protein be produced from a bacterial colony containing the gene of interest?
Put a cDNA encoding the protein into a plasmid with a bacterial promoter sequence.; Once a cDNA is put into a plasmid with a bacterial promoter, the bacteria will transcribe and translate the gene.
In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, what was the key finding?
Radioactively labeled phosphorus was present inside the infected bacteria; When the bacteria had been infected with T2 phage whose DNA was tagged with radioactive phosphorus, the pellet of mainly bacterial material contained most of the radioactivity, indicating that the labeled phage DNA had entered the cells.
Drag the labels to their appropriate locations in the flowchart below, indicating the sequence of events in the production of fragment B. (Note that pol I stands for DNA polymerase I, and pol III stands for DNA polymerase III.)
Synthesis of the lagging strand is accomplished through the repetition of the following steps. Step 1: A new fragment begins with DNA polymerase III binding to the 3' end of the most recently produced RNA primer, primer B in this case, which is closest to the replication fork. DNA pol III then adds DNA nucleotides in the 5' to 3' direction until it encounters the previous RNA primer, primer A. Step 2: DNA pol III falls off and is replaced by DNA pol I. Starting at the 5' end of primer A, DNA pol I removes each RNA nucleotide and replaces it with the corresponding DNA nucleotide. (DNA pol I adds the nucleotides to the 3' end of fragment B.) When it encounters the 5' end of fragment A, DNA pol I falls off, leaving a gap in the sugar-phosphate backbone between fragments A and B. Step 3: DNA ligase closes the gap between fragments A and B. These steps will be repeated as the replication fork opens up. Try to visualize primer C being produced to the right (closest to the replication fork). Fragment C would be synthesized and joined to fragment B following the steps described here.
The DNA double helix is composed of two strands of DNA; each strand is a polymer of DNA nucleotides. Each nucleotide consists of a sugar, a phosphate group, and one of four nitrogenous bases. The structure and orientation of the two strands are important to understanding DNA replication.
The DNA double helix is constructed from two strands of DNA, each with a sugar-phosphate backbone and nitrogenous bases that form hydrogen bonds, holding the two strands together. Each DNA strand has two unique ends. The 3' end has a hydroxyl (-OH) group on the deoxyribose sugar, whereas the 5' end has a phosphate group. In the double helix, the two strands are antiparallel, that is, they run in opposite directions such that the 3' end of one strand is adjacent to the 5' end of the other strand.
If a cell were unable to produce histone proteins, which of the following would be a likely effect?
The cell's DNA couldn't be packed into its nucleus.
How does the company raising these fish claim to prevent the genetically modified fish from breeding with wild fish?
The genetically modified fish are sterile.
This is an animation of gel electrophoresis. Which of these DNA molecules is the shortest?
The shorter the DNA molecule, the farther it moves.
Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?
The transferred traits were heritable; The fact that offspring of transformed bacteria also showed the pathogenic trait meant that the transforming agent had to be involved with the genetic material.
Studies of nucleosomes have shown that histones (except H1) exist in each nucleosome as two kinds of tetramers: one of 2 H2A molecules and 2 H2B molecules, and the other as 2 H3 and 2 H4 molecules. Which of the following is supported by this data?
The two types of tetramers associate to form an octamer.
What information can not be obtained from the sequence of a gene?
Whether the gene is methylated.; Although the gene's sequence may reveal the presence of methylation targets like cytosine (C), it does not give information about whether such bases have been methylated.
Which of the following modifications is least likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?
altering the nucleotide sequence of the DNA fragment without adding or removing nucleotides
Individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells are impaired in what way?
They cannot repair thymine dimers.
What concerns do some consumer groups have about genetically modified fish?
They want more studies on the health effects that genetically modified fish may have on people who eat it. They want food from genetically modified fish to be clearly labeled as genetically modified. They want to prevent genetically modified fish from breeding with wild fish.
To accomplish the screening, researchers synthesize a single-stranded DNA probe using vgp mRNA as a template. What will be the sequence of nucleotides in the probe?
To screen a library of bacterial colonies for clones that carry a specific gene, a relatively short, single-stranded nucleic acid probe is hybridized to the DNA of that gene. Often, the probe is a DNA strand synthesized by reverse transcriptase from the mRNA encoded by the gene. Bases in the probe hydrogen-bond to complementary bases in the gene. If the probe has been labeled with a radioactive isotope or a fluorescent tag, researchers can identify the bacterial clones that contain the DNA to which the probe has bound. Those clones can be grown in large quantities, allowing many copies of the gene to be isolated for use in research or other applications.
transformation
Transformation is the process by which a bacterium takes up a plasmid from the surrounding solution.
True or false? Comparison of the sequences of the same gene across species can give some insight into the existence of a common ancestor with that gene.
True; DNA sequence comparisons are a powerful tool by which to estimate how closely related different species are along the evolutionary timeline.
True or false? The term "sticky ends" refers to the overhanging ends on DNA that are generated by restriction enzymes, which can base pair with any DNA molecules that contain complementary sticky ends.
True; Restriction enzymes cut DNA and generate "sticky ends," which can then base pair with DNA molecules that contain the same sticky ends.
Hershey and Chase used _____ to radioactively label the T2 phage's proteins.
^35S, Hershey and Chase used radioactive sulfur to label the phage's proteins
In recombinant DNA experiments, what is used to cut pieces of DNA and what joins the resulting fragments to form recombinant DNA?
a restriction enzyme ... DNA ligase Restriction enzymes cut DNA molecules at specific points; in most cases, the restriction fragments have sticky ends that can base-pair with complementary sticky ends. The joined segments are then covalently fused by DNA ligase.
Assume that you are trying to insert a gene into a plasmid. Someone gives you a preparation of genomic DNA that has been cut with restriction enzyme X. The gene you wish to insert has sites on both ends for cutting by restriction enzyme Y. You have a plasmid with a single site for Y, but not for X. Your strategy should be to
cut the DNA again with restriction enzyme Y and insert these fragments into the plasmid cut with the same enzyme
Which of the following sets of materials is required by both eukaryotes and prokaryotes for replication?
double-stranded DNA, four kinds of dNTPs, primers, origins
To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
endonuclease, DNA polymerase I, DNA ligase
The research showed that individuals who _______ had younger looking cells based on telomere measurements.
exercised for an average of 30 minutes per day
The fish in the video have been genetically engineered to _____.
grow faster
I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes separates the DNA strands during replication?
helicase
A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics. Bacteria that contain the plasmid, but not the eukaryotic gene, would grow
in all four types of broth.
A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics. Bacteria containing a plasmid into which the eukaryotic gene has integrated would grow
in the ampicillin broth and the nutrient broth.
Which of the following damages cells and causes cell aging?
inflammation
Which of the following is an example of "recombinant DNA technology?"
introducing a human gene into a bacterial plasmid Recombinant DNA technology involves combining DNA from different sources into a single molecule, such as inserting a gene from one species into a plasmid from another.
The reason for using Taq polymerase for PCR is that
it is heat stable and can withstand the temperature changes of the cycler.
After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained _____, which demonstrated that _____ is the phage's genetic material.
labeled DNA ... DNA, Since the phage DNA entered the infected cell, it makes sense that DNA is the genetic material.
Gel electrophoresis separates DNA fragments on the basis of what characteristic?
length; As the DNA fragments move through the gel, longer fragments are impeded more than shorter fragments, producing characteristic banded patterns in the gel.
I. helicase II. DNA polymerase III III. ligase IV. DNA polymerase I V. primase Which of the enzymes covalently connects segments of DNA?
ligase
The researchers found that telomeres were ______.
longer in individuals who exercised regularly
According to the producers of the genetically modified salmon, the meat _____.
looks and tastes the same as unmodified salmon
Research indicates that the best estimate of your age is from ______.
markers in your cells
Which of the following represents the order of increasingly higher levels of organization of chromatin?
nucleosome, 30-nm chromatin fiber, looped domain
What process repairs damage to a preexisting double helix?
nucleotide excision repair; In nucleotide excision repair, a section of DNA containing the damage is removed, and the gap is then filled in and completed by DNA polymerase and DNA ligase.
This is an image of a _____.
phage, This is a T2 phage, a type of phage that infects E. coli.
It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information in which of the following?
sequence of bases
Which of the following help(s) to hold the DNA strands apart while they are being replicated?
single-strand binding proteins
The unpaired nucleotides produced by the action of restriction enzymes are referred to as _____.
sticky ends They are called sticky ends since they will "stick" to a complementary single-stranded sequence.
In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding?
the 30-nm chromatin fiber
What is the most commonly used vector for introducing transgenes into plants?
the Ti plasmid; The Ti plasmid comes from Agrobacterium tumefaciens, and it is effective at integrating with the host cell's DNA.
Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA?
the diameter of the helix
The leading and the lagging strands differ in that
the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.
The difference between ATP and the nucleoside triphosphates used during DNA synthesis is that
the nucleoside triphosphates have the sugar deoxyribose; ATP has the sugar ribose.
A eukaryotic gene has "sticky ends" produced by the restriction endonuclease EcoRI. The gene is added to a mixture containing EcoRI and a bacterial plasmid that carries two genes conferring resistance to ampicillin and tetracycline. The plasmid has one recognition site for EcoRI located in the tetracycline resistance gene. This mixture is incubated for several hours, exposed to DNA ligase, and then added to bacteria growing in nutrient broth. The bacteria are allowed to grow overnight and are streaked on a plate using a technique that produces isolated colonies that are clones of the original. Samples of these colonies are then grown in four different media: nutrient broth plus ampicillin, nutrient broth plus tetracycline, nutrient broth plus ampicillin and tetracycline, and nutrient broth without antibiotics. Bacteria that do not take up any plasmids would grow on which media?
the nutrient broth only
What is the function of DNA polymerase III?
to add nucleotides to the 3' end of a growing DNA strand
Use the following information to answer the next few questions. A group of six students has taken samples of their own cheek cells, purified the DNA, and used a restriction enzyme known to cut at zero, one, or two sites in a particular gene of interest. Why might they be conducting such an experiment?
to find which of the students has which alleles
