life 120 chapter 13
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
The elongation of the leading strand during DNA synthesis
depends on the action of DNA polymerase
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
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 of repliaction
To repair a thymine-dimer by nucleotide excision repair, in which order do the necessary enzymes act
endonuclease, DNA polymerase I, DNA ligase
What is the most logical sequence of steps for splicing foreign DNA into a plasmid and inserting the plasmid into a bacterium
extract the plasmid DNA from bacerial cells, cut the plasmid DNA using restriction enzymes, hydrogen-bond the plasmid DNA to nonplasmid DNA fragments, use ligase to seal plasmid DNA, transform the bacteria with a recombinant DNA molecule
Which of the enzymes separates the DNA strands during replication
helicase
Which of the following statements describes chromatin
heterochromatin and euchromatin are found in the cytoplasm
In a nucleosome, the DNA is wrapped around
histones
Why do histones bind tightly to DNA
histones are positively charged, and DNA is negatively charged
Bacteria that contain the plasmid, but not the eukaryotic gene, would grow
in all four types of broth
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 statements describes the eukaryotic chromosome
it consists of a single linear molecule of double-stranded DNA plus proteins
The reason for using Taq polymerase for PCR is that
it is heat stable and can withstand the heating step of PCR
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
leading strands and Okazaki fragments
which of the enzymes covalently connects segments of DNA
ligase
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
The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine an uncommon base, opposite thymine. What combination of proteins could repair such damage?
nuclease, DNA polymerase, DNA ligase
Which of the following represents the order of increasingly higher levels of organization of chromatin
nucleosome, 30-nm chromatin fiber, looped domain
which of the enzymes synthesizes short segments of RNA
primase
What is the function of topoisomerase
relieving strain in the DNA ahead of the replication fork
One the patter found after one round of repliation was observed, Meselson and Stahl could be confident of which of the following conclusions
replication is not conservative
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
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
In his work with pneumonia-causing bacteria and mice, Griffith found that
some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic
In a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding
the 30-nm chromatin fiber
What is meant by the description "antiparallel" regarding the strands that make up DNA
the 5' to 3' direction of one strand runs counter to the 5' to 3' direction of the other strand
given the damage caused by UV radiation, the kind of gene affected in those with XP is one whose product is involved with
the ability to excise single-strand damage and replace it
If a cell were unable to produce histone proteins, which of the following would be a likely effect
the cell's DNA couldnt be packed into its nucleus
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
Bacteria that do not take up any plasmids would grow on which media
the nutrient broth only
Analysis of the data obtained from the cheek experiment shows that two dtudents each have two fragments, two students each have three fragments, and two students each have one only. What does this demonstrate
the two students who have two fragments have one restriction site in this region
In an experiment DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP and radioactively labeled dTTP (3H thymidine) after several minutes, the DNA is switched to nonradioactive medium and is then viewed by electron microscopy and autoradiography. Figure 13.2 represents the results. It shows a replication bubble, and the dots represent radioactive material. Which of the following is the most likely interpretation of the results
there are two replication forks going in opposite directions
A group of 6 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 have which alleles
In an analysis of the nucleotide composition of DNA, which of the following will be found
A + C = G + T
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules
A + G = C + T
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Why wont this experiment work
Amino acids, and thus proteins, also have nitrogen atoms; thus the radioactivity would not distinguish between DNA and proteins
Which of the results in Figure 13.1 would you expect if the DNA was replicated in a conservative manner
B (2 strands, far apart, one heavy)
The segment of DNA shown in Figure 13.4 has restriction sites I and II, which create restriction fragment A, B and C. Which of the gels produced by electrophoresis shown below best represents the separation and identity of these fragments
B (B is the shortest so it moves the farthest, A is next shorest moves the second farthest, C is the longest and moves the shortest distance)
In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which result would be expected after one round of DNA replication
D (one strand, in the middle)
In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts
DNA contains phosphorus, whereas protein does not
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
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
DNA ligase
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
What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized
DNA polymerase can join new nucleotides only to the 3' end of a growing strand
A new DNA strand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end
Which of the following investgators 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
Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme
GGCC CCGG
Which of the following statements is true about histones
Histone H1 is not present in the nucleosome bead; instead, it draws the nucleosomes together
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication
It joings Okazaki fragments together
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 DNA replication fork will be formed
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two or more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What does density distribution of DNA would you expect in this experiment
One low-density and one intermediate-density band
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
Studies of nucleosomes have shown that histones (excpet 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
why is it so importnt to be able to amplify DNA fragments when studying genes
a gene may represent only a millionth of the cell's DNA
Which enzyme was used to produce the molecule in figure 13.3
a restriction enzyme
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
How do we describe transformation in bacteria
assimilation of external DNA into a cell
how does a bacterial cell protect its own DNA from restriction enzymes?
by adding methyl groups to adenines and cytosines
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 stating at the 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%
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 is the function of DNA polymerase III
To add nucleotides to the 3' end of a growing DNA strand
