biology chapter 16
As a result of proofreading by DNA polymerase, the overall error rate in the completed DNA molecule is approximately ___
1 error per 10 billion
In a nucleotide, the nitrogenous base is attached to the sugar's ___ carbon and the phosphate group is attached to the sugar's ___ carbon
1',5'
What is the correct model of DNA replication? Describe it
1. DNA is unzipped by an enzyme called helicase. (all enzymes end in -ase and that the enzyme responsible for unzipping the DNA is called "helic"ase because it acts on the helical strucute of DNA) 2. The enzyme DNA polymerase moves in and fills in the complimentary sequence of nucleotides on each of the parent strands. 3. The two developing DNA strands separate into two new DNA strands.
DNA polymerase adds nucleotides to the ___ of the leading strands, and to the ___ of the lagging strands.
3'end
Hersey and Chase used ___ to radioactively label the T2 phage's proteins
35S
Nucleic acids are assembled in the ___ direction
5' to 3'
DNA is always added from the _____ end to the _____ end on the growing strand
5', 3'
Describe the structure of a nucleosome, the basic unit of DNA packing in eukaryotic cells
A nucleosome is made up of eight histone proteins, two each of four different types, around which DNA is wound. Linker DNA runs from one nucleosome to the next
In DNA, the 2 purines are ___, and the 2 pyrimidines are ___
Adenine and guanine, cytosine and thymine
Who demonstrated that DNA that DNA is the genetic material of a T2
Alfred Hersey and Martha Chase
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. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
In any species there is an equal number of A and T bases, and an equal number of G and C bases
Chargaff's rule
What role does complementary base pairing play in the replication of DNA?
Complementary base pairing ensures that the two daughter molecules are exact copies of the parental molecule. When the two strands of the parental molecule separate, each serves as a template on which nucleotides are arranged, by the basepairing rules, into new complementary strands.
The radioactive isotope 32P labels T2 phage's ___
DNA
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
What enzyme joins Okazaki fragments
DNA ligase
Identify 2 major functions of DNA pol III in DNA replication.
DNA pol III covalently adds nucleotides to new DNA strands and proofreads each added nucleotide for correct base pairing.
The enzyme that can replicate DNA is called ___
DNA polymerase
What catalyzes DNA synthesis?
DNA polymerase
an enzyme that catalyzes the elongation of new DNA
DNA polymerase
The removal of the RNA primer and addition of DNA nucleotides to the 3'end of Okazaki fragments in its place is carried out by ___
DNA polymerase I
Which enzyme catalyzes the elongation of a DNA strand in the 5' → 3' direction?
DNA polymerase III
Why is the new DNA strand complementary to the 3'to 5'strand assembled in short segments
DNA polymerase can assemble DNA only in the 5'to 3'direction
What is the basis for the differance 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 pre-existing strand
The process by which a DNA molecule is copied
DNA replication
Meselson and Stahl cultured E. coli for several generations in a medium with a heavy isotope of nitrogen, 15N. They transferred the bacteria to a medium with a light isotope of nitrogen, 14 N. After two rounds of DNA replication, half the DNA molecules were light (both strands had 14N) and half were hybrids (15N-14N). What did the researchers conclude from these results?
DNA replication is semiconservative
During DNA replication, the leading stran is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?
DNA synthesis can take place only in the 5' to 3' direction
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?
Descendents of the living cells are also phosphorescent
Which of the following statements about replication origins is/are correct a) bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins b) The 2 strands of DNA at the origin of replication are separated, creating a replication bubble c) Replication proceeds in both directions from each origin d) the DNA sequence at the origin of replication is replication is recognized by specific proteins that bind to the origin e) all the listed responses are correct
E
DNA replication is said to be semiconservative. What does this mean?
Each new double helix consists of one old and one new strand.
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
Who reported that DNA composition varied from one species to the next
Erwin Chargaff
What two properties, one structural and one functional, distinguish heterochromatin from euchromatin?
Euchromatin is chromatin that becomes less compacted during interphase and is accessible to the cellular machinery responsible for gene activity. Heterochromatin, on the other hand, remains quite condensed during interphase and contains genes that are largely inaccessible to this machinery.
Who first discovered transformation
Frederick Griffith
Who demonstrated that DNA is the genetic material of the T2 phage
Hersey and Chase
Nucleotides are added to a growing DNA strand as nucleoside triosphates. What is the significance of this fact?
Hydrolysis of the 2 phosphate groups and DNA poylmerization are a coupled exergonic reaction
What is the relationship between DNA replication and the S phase of the cell cycle?
In the cell cycle, DNA synthesis occurs during the S phase, between the G1 and G2 phases of interphase. DNA replication is therefore complete before the mitotic phase begins.
How does the enzyme telomerase meet the challenge of replicating the ends of linear chromosomes?
It catalyzes the lengthening of telomeres, compensating for the shortening that occurs during replication.
Who created a double-helicai model for the structure of DNA
James watson and Francis Crick
Although the proteins that cause the E. coli chromosome to coil are not histones, what property would you expect them to share with histones, given their ability to bind to DNA
Like histones, the E. coli proteins would be expected to contain many basic (positively charged) amino acids, such as lysine and arginine, which can form weak bonds with the negatively charged phosphate groups on the sugar-phosphate backbone of the DNA molecule.
The researcher 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
Who used X-ray crystallography to study molecular structure
Maurice Wilkins and Rosalind Franklin
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 from
a short segment of DNA synthesized away from the replication fork on a template strand during DNA replecation
Okazaki fragment
___ are the shortest sections of DNA that are synthesized on the lagging strand of the replicating DNA
Okazaki fragments
Which part of a deoxynucleoside (dNTP) molecule provides the energy for DNA
Phosphate groups
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.
Which of the following components is required for DNA replication?
RNA primer
The synthesis of a new strand begins with the synthesis of a(n) ___
RNA primer complementary to a preexisting DNA strand
In the Hersey 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
Once the DNA at the replication fork is unwound by helicases, what prevents the 2 strands from coming back together to re-form a double helix?
Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming
Who discovered where genes are located
T.H, Morgan
One strand of a DNA molecule has the base sequence 5'-ATGGT_3'. The complementary base sequence on the other strand of DNA will be 3'- ___-5".
TATCCA
The enzyme _______ is used to replicate telomeres but is only found in _________________ cells.
Telomerase , (fetal tissues, adult germ cells, and also tumor cells.)
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.
DNA is a self-replicating molecule. What accounts for this important property of DNA?
The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C
Interphase chromosomes appear to be attached to the nuclear lamina and perhaps also the nuclear matrix. Describe these two structures.
The nuclear lamina is a netlike array of protein filaments that provides mechanical support just inside the nuclear envelope and thus maintains the shape of the nucleus. Considerable evidence also supports the existence of a nuclear matrix, a framework of protein fibers extending throughout the nuclear interior.
Griffith's experiment with S. pneumoniae were significant because they showed that traits could be transformed from one organism to another. What else did he find that was significant>
The transferred traits were heritable
helps relieve the strain by breaking, swiveling, and rejoining DNA strands
Topoisomers
Who is credited with explaining the structure of the DNA double helix
Watson and Crick
Given a polynucleotide sequence such as GAATTC, can you tell which is the 5'end? If not what further information do you need to identify the ends?
You can't tell which end is the 5′ end. You need to know which end has a phosphate group on the 5′ carbon (the 5′ end) or which end has an ¬OH group on the 3′ carbon (the 3′ end).
Which of the following statements about Okazaki fragments in E. coli is true a) They are formed on the lagging strand of DNA b) They are synthesized in the 3' to 5' direction c) They are usually 50' to 500 bases long d) They are sealed together by the action of helicase
a
Which one of the following statements is correct a) Adenine forms 2 hydrogen bonds with thymine: guanine forms 3 hydrogen bonds with cytosine b) Adenine forms 2 hydrogen bonds with thymine; guanine forms 2 hydrogen binds with cytosine c) Adenine forms 2 hydrogen binds with guanine, thymine forms binds 3 hydrogen binds with cytosine d) Adenine forms 3 covalent bonds with thymine, guanine forms 2 covalent binds with cytosine e) adenine forms 2 covalent bonds with thymine, guanine forms 3 cocavalent bonds with cytosine
a
Which one of the following statements regarding DNA replication is correct a) Helicases separate the 2 strands of the double helix, and DNA polymerases then construct 2 new strands using each of the original strands as templates b) The 2 strands separate, and each one receives a complementary strand of RNA. Then this RNA serves as a template for the assembly of many new strands of DNA c) Ligase separate the 2 strands of DNA separate, and nuclease enzymes digest one strand. Then, DNA polymerase synthesizes 2 new strands out of the old ones. d) Liagase assembles nucleotides into Okazaki fragments. Then polymerase joins these fragments together into a DNA strand The 2 strands of DNA separate, and nuclease enzymes digest one strand. Then, DNA polymerase synthesizes 2 new strands out of the old ones.
a
Which of the following would you expect of a eukaryote lacking telomerase?
a reduction in chromosome length in gametes
At each end of a DNA replication bubble is ___
a replication bubble
How do we describe transformation in bacteria
assimilation of external DNA into a cell
The role of DNA polymerases in DNA replication is to
attach free nucleotides to the new DNA strand
In analyzing the number of differant bases in a DNA sample, which result would be consistent with the base-pairing rules? a) a=G b) A+G=C+T c) A+T=G+C d) A=C
b
Which of the following statements about DNA synthesis is true? a) Nucleotides are added in a random fashion to single-stranded DNA Primers are short sequences that allow the initiation of DNA synthesis c) As DNA poylmerase moves along the template strand, each new nucleotide provides a 5' hydroxyl group for the next reaction to occur d) DNA poylmerase adds dNTP monomers in the 3'to 5' direction
b
What is the major difference between bacterial chromosomes and eukaryotic chromosomes
bacteria usually have a single circular chromosomes whereas eukaryotes have several linear chromosomes
bacteria eating
bacteriophages
The cells examined from the 2,400 people in this study were from ___
blood
During the replication of DNA, ____
both strands of a molecule as templates
In a comparison between asexually reproducing bacteria and sexually reproducing multicellular eukaryotes, uncorrected errors in replication are more likely to be transmitted to subsequent generations in bacteria than in multicellular eukaryotes. Which of the following provides the best evidence-based explanation for this difference? a)Unlike multicellular eukaryotes, bacteria lack DNA repair enzymes, so there are just more uncorrected errors at play. b) Although the genome for each is represented as pairs of homologous chromosomes, errors in bacteria affect both homologs, but only one is affected in eukaryotes c) because they are asexual and single-celled, all uncorrected errors of replication in bacteria are transmitted to subsequent generations. Multicellulr eukaryotes typically reproduce sexually, so uncorrected errors are transmitted only if they occur in germ cells that meiotically divide to produce gamates. d) only errors that lead to faster growing strains are left uncorrected in bacteria, whereas all errors are detected and repaired in multicellular eukaryotes e) The third and fourth listed responses can explain this phenomenon
c
In trying to determine whether DNA or protein is the gen tic material, Hersey and Chase made use of which of the following facts? a) RNA includes ribose, whereas DNA includes deoxyribose sugars b) DNA contains purines, whereas protein includes pyrimidines c) DNA contains phosphorus, whereas whereas protein does not d) DNA contains nitrogen whereas protein does not e) DNA contains sulfur, whereas protein does not
c
Which of these nitrogenous bases is found in DNA but not in RNA a) uracil b) guanine c) thymine d) cytosine e) adenine
c
The incorporation of an incorrect base into the DNA during replication ___
can be repaired by the mismatch repair system
Unlike prokaryotic replication, replication of eukaryotic chromosomes
cannot be completed by DNA polymerse
A ______ consists of a DNA molecule packed together with __________________.
chromosome, proteins
Which of these is a difference between a DNA and an RNA molecule a) DNA contains nitrogenous bases, whereas RNA contains phosphate groups b) DNA contains uracil, whereas RNA contains thymine c) DNA contains f-carbon sugars, whereas RNA contains 6-carbon sugars d) DNA is usually double-stranded, whereas RNA is usually single-stranded e) DNA is polymer composed of nucleotides, whereas RNA is a polymer composed of nucleic acid
d
supplies adenine to DNA and is similar to the ATP of energy metabbolism
dATP
After replication is complete, the new DNAs called ___, are identical to each other
daughter DNA
nucleotide=___+___+___
deoxyribise+phosphate+base
The elongation of the leading strand during DNA synthesis
depends on the action of DNA polymerase
the presence of 2 strands
double helix
Which of the following considerations was/were important in the choice of viruses and bacteria for early experiments on DNA? a) they have shorter generation times b) their chromosomes have a simpler structure c) The can interact with each other d) they typically have relitively small genomes e) all of the above
e
Which of the following statements is/are correct with regard to individuals with the disorder xeroderma pigmentosium a) these individuals have high rates of skin cancer b) cells in these individuals have difficulty have repairing thymine dimers c) these individuals usually have inherited defects in the nucleotide excision repair system d) These individuals are extremely sensitive to sunlight e) all the aboce
e
After DNA replication is completed ___
each new DNA helix consists of 2 old strands and one DNA double helix consists of 2 new strands
loosely packed cjromatin
euchromatin
the less condensed form of eukaryotic chromatin chromatin that is available for transcription
euchromatin
The research showed that individuals who ___ had younger looking cells based on telomere measurments
exercised for an average of 30 minutes per day
Telomeres ____
get shorter with each round of DNA replication
During Griffith's experiment with Streptococcus pneumonia in mice, material from ___ bacteria transformed ___ bacteria.
heat-killed pathogenic, living nonpathogenic
The first step in the replication of DNA is catalyzed by ___
helicase
breaks H-bonds between bases binds at the replication fork
helicase
After the formation of a replication bubble, which of the following is the correct sequence of enzyme used for the synthesis of the lagging DNA strand?
helicase, primase, DNA polymerase, ligase
Enzymes that untwist the double helix at the replication forks
helicases
eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed
heterochromatin
In a nucleosome, the DNA is wrapped around
histones
responsible for the first level of DNA packing in chromatin
histones
What types of bonds hold the two strands of DNA together
hydrogen bonds
The 2 antiparallel strands of nucleotides that form the DNA double helix are held together by
hydrogen bonds between nucleotides bases
Which of the following damages cells and causes cell aging? a) inflammation b) reducing stress c) exercise d) all of the above
inflamation
Telomerase ___
is an enzyme that lengthens telomeres
Which of the following attributes of DNA is most crucial to its accurate duplication
its specific base pairing through hydrogen bonds
After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hersey 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
A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments away from the replication fork
lagging strand
multiple primers needed made in segments daughter elongates away from replication fork
lagging strand
The new DNA strand that grows continuously in the 5'to 3; direction is called ___
leading strand
made continuously only one primer needed daughter strand elongates toward replication fork
leading strand
the new complementary DNA strand synthesized continuously along the template toward replication fork in the mandatory 5'-3'
leading strand
Short segments of newly synthesized DNA are joined into a continuous strand by ___
ligase
The research showed that telomeres were ___
longer in individuals who exercised regularly
Research indicates that the best estimate of your age is from ___
markers in your cells
Damaged or otherwise mismatched areas may be repaired by ______________.
mismatch repair
the cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides
mismatch repair
In prokaryotes, the rate of elongation during DNA replication is ___ the rate in eukaryotes
much faster than
an enzyme that cuts DNA or RNA
nuclease
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 set of enzymes is involved in nucleotides excision repair
nuclease, DNA polymerase, and ligase
each nucleotide that is added to a growing DNA strand is called
nucleoside triphosphate
the basic bead-like unit of DNA packing in eukaryotes
nucleosome
In the "beads on a string"structure of unfolded chromatin, the "beads"are ___
nucleosomes
a repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide
nucleotide exicision repair
Monomers of the synthesis of DNA are called ___
nucleotides
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
one low density and one intermediate density
the site where replication of a chromosome begins
orgins of replication
Which of the following enzymes creates a primer for DNA polymerase
primase
an enzyme that joins RNA nucleotides to make a primer
primase
a short stretch of RNA with a free 3'end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication
primer
Until Hersey and chase showed that DNA was the genetic molecule of the phages they studied, what class of molecules was considered the best candidate for carrying genetic information and why?
proteins because they were thought to be the only molecule with both the variety and specificity of function to account for the array of heritable traits observed
Name and describe the 2 types of nitrogenous bases
purines A and G pyrimidines C and T and U
The experiments of Meselson and Stahl showed that DNA ___
replicates in a semiconservative fasion
During DNA replication, an open section of DNA, in which a DNA polymerase can replicate DNA, is called a ___
replication fork
a y-shaped region at the end of a replication bubble
replication fork
The action of helicase creates ___
replication forks and replication bubbles
binds after the replication fork prevents H-bonds between bases
single-strand binding protein
In his work with pneumonia-causing bacteria and mice, Griffith found that
some substances from pathogenic cells cause pneumonia
What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?
telomeres
An old DNA strand is used as a ___ for the assembly of a new DNA strand
template
The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?
that the critical function of telomeres must be maintained
In an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial, the phage contained radioactive DNA, and radioactivity was detected inside the vateria. Next, phage-containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that ___.
the genetic material of the phage is DNA
short RNA primer
the initial nucleotide
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 scientist assembles a bacteriophages with protein coat of a phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have ___
the protein and DNA of T4
Chargaff found for DNA ___
the ratio of A-T is close to 1:1 and the ration of G-C is close to 1:1
The information in DNA is contain in ___
the sequence of nucleotides along the length of the 2 strands of the DNA molecule
In DNA double helix an adenine of one strand always pairs with a(n) ___ of the complementary strand, and a guanine of one strand always pair with a(n) of the complementary strand
thymine, cytosine
In a DNA double helix an adenine of one strand always pair with a(n) ___ of the complementary strand, and a guanine of one strand always pair with a(n) ___ of the complementary strand
thymine, cytosine
The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is revealed by an enzyme called
topoisimerase
What enzyme is important for relieving the tension in a helix as it unwinds during DNA synthesis
topoisomerase
binds ahead of the replication fork breaks covalent bonds in DNA backbone
topoisomerase
True or False? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but orient in opposite directions
true
an infectious particle incapable of replicating outside of a cell, consisting of an RNA or DNA genome surrounded by a protein coat
virus
Avery and his colleagues'1944 experiment showed that DNA ___
was the substance that transformed the bacteria in Griffith's experiment
Which of the following techniques was the most helpful to Watson and Crick in developing their model for the structure of DNA
x-ray crystallography
