Chapter 14 smart Book
How many hydrogen bonds are formed between adenine and thymine in the double DNA helix?
2
Which of these best describes the density of the bacterial DNA after the second round of replication in the Meselson-Stahl experiments?
2 density classes - one intermediate and one 14N DNA
Guanine forms___________ hydrogen bonds with cytosine.
3
How many hydrogen bonds form between cytosine and guanine in the DNA double helix?
3
Chargaff's rule indicates that the amount of A in a sample is equal to the amount of (blank) and the amount of C in a sample is equal to the amount of (blank).
Blank 1: T or thymine Blank 2: G or guanine
--------------are short protective repeats of DNA on the ends on eukaryotic chromosomes which are generated by the enzyme--------
Blank 1: Telomeres Blank 2: telomerase
In DNA, consecutive nucleotides are linked via (blank) bonds, which are made between the 5' phosphate of one nucleotide and the 3' (blank) group of another nucleotide.
Blank 1: phosphodiester Blank 2: hydroxyl or OH
Which of the following facilitates the reversal of damage to our hereditary material before a permanent mutation can occur?
DNA repair systems
The experiments used to distinguish between the three potential DNA replication mechanisms were performed by
Meselson and Stahl.
_____________ repair is responsible for removing bases that were incorrectly incorporated into DNA during replication.
Mismatch
What type of repair mechanism is responsible for removing bases that were incorrectly inserted into DNA during replication?
Mismatch repair
Which of these is not required for DNA replication?
NADPH
Short fragments of DNA created on the lagging strand of DNA during replication are called
Okazaki fragments
What is the name of the subunit that acts as the sliding clamp, which keeps the replicating enzyme complex attached to the template in eukaryotic cells.
PCNA
Which enzymes did Avery, MacLeod, and McCarty use in order to identify the genetic material?
RNA digesting enzymes protein digesting enzymes DNA digesting enzymes
Consider a double stranded DNA molecule. In complementary base pairing, A pairs with_____________ and C pairs with___________.
T,G
Which enzyme prevents chromosomal shortening by attaching a repeat sequence to the ends of chromosomes?
Telomerase
What is the name of the regions at the ends of eukaryotic chromosomes?
Telomeres
Which of the following are short repeats of DNA on the ends of eukaryotic chromosomes?
Telomeres
During the synthesis of the new DNA molecule, where are the new nucleotides added by DNA polymerase?
The 3' end of the growing strand
The appearance of colonies of Streptococcus pneumoniae is related to the presence or absence of
a polysaccharide coat
Bacterial replication (for example in E. coli) begins at
a single origin
Cells have several non-specific repair pathways. Indicate which of the following are two general categories of repair mechanisms:
error-free error-prone
In E. coli, the SOS response is part of the
error-prone repair mechanism
Based on replication proteins, DNA replication in archaea is most similar to that of
eukaryotes
Cancer cells contain
higher levels of telomerase than normal, non-cancer cells.
The sliding clamp of a DNA polymerase
holds the polymerase to the DNA template
The primary purpose of the Meselson and Stahl experiments was to determine
how DNA replicates.
The topological state of DNA refers to
how the DNA coils
Regarding Meselson and Stahl's experiment, the primary difference between the proposed models of DNA replication was related to
how the parental strands were incorporated into the daughter strands
DNA replication in eukaryotic cells is complicated by the fact that eukaryotic cells have
linear chromosomes
In an aging cell, the activity of telomerase would be
low
The level of telomerase stays high in ______, despite their age.
lymphocytes
DNA primase (choose all that apply)
makes a primer of RNA complementary to the DNA. makes a primer about 10 -20 nucleotides in length.
During semiconservative DNA replication
one of the strands in each new double helix comes from the original molecule, and one is newly synthesized.
Which origins are more sequence-specific?
oriC
Adjacent nucleotides in the same DNA strand are held together by covalent bonds known as_______________ bonds.
phosphodiester
Repeating sugar and phosphate units in a single DNA strand make up the
phosphodiester backbone.
Damage caused by UV light leading to thymine dimers is corrected during photorepair by the enzyme ______.
photolyase
The enzyme _________ can repair UV damage by binding to a thymine dimer and cleaving it, therefore restoring two thymines
photolyase
The enzyme DNA _____ covalently links nucleotides to synthesize new DNA strands together during DNA replication.
polymerase
The enzyme DNA ____________ synthesizes the RNA primers required by DNA polymerases during replication.
primase
All DNA polymerases require a short strand of DNA or RNA, called a__________ to begin their synthesis
primer
In the replisome, the ___________is composed of primase, helicase, and accessory proteins that prime the lagging strand.
primosome
Interpretation of the Meselson-Stahl data leads to support of this model of DNA replication
semiconservative
DNA replication that leads to the production of double helices with one parental strand and one newly synthesized strand is consistent with
semiconservative replication
Place the steps of lagging strand synthesis in the correct order (start at the top)
synthesize primers using primasesynthesize DNAreplace RNA primers with DNAseal nicks in the DNA
The amount of the enzyme-----------declines within cells as they age.
telomerase
The enzyme__________ contains a small internal piece of RNA, which is used as a template to extend the end of a linear DNA molecule.
telomerase
Short, repeated sequences of DNA are characteristic of
telomeres
DNA replication in E. coli ends at a site called the_________
terminus
Griffith's experiments were important because they showed
that the genetic material could be passed from one cell to another
In nucleic acids, the prime symbol is used to indicate
the carbon in a sugar rather than the atoms in the bases attached to the sugars
If normal fibroblast cells are grown in cell culture and the enzyme telomerase is introduced in them,
the cells show an increased lifespan
The problems in replicating the ends of linear chromosomes are caused by (choose all that apply)
the directionality of polymerases the need for a primer
The enzymes in the replisome are active on
the leading and the lagging strands
The partial opening of a DNA helix to form two single strands is called
the replication fork
DNA repair mechanisms have likely evolved because
there is no way for cells to avoid exposure to mutagens
Franklin determined that the structure of DNA was helical based on
x-ray diffraction analysis
Match the function of each DNA polymerase in E. coli.
- I - acts on the lagging strand to remove primers and replace them with the DNA II - not involved in replication but used for DNA repair III - the main replication enzyme
Match these enzymes involved in DNA replication with their function. Helicase Gyrase Primase Polymerase
- Unwinds the double helix -relieves coiling in the DNA strand ahead of the replication fork -Makes a 10-12 bp complimentary primer to the DNA -attaches a nucleotide to the 3' end of the DNA strand
Match the following strands with the type of synthesis. Leading Strand Lagging Strand
-Synthesized continuously -Synthesized in small fragments that are later connected
Match each element of the nucleotide to the sugar carbon atom it is attached to.
1'nitrogenous base3'OH group5'phosphate group
Order the steps in excision repair from first to last, starting at the top.
1. Recognition of damage 2. Removal of the damaged region 3. Resynthesis using the information on the un damaged strand as a template
In the Meselson-Stahl experiment, what was the expected composition of DNA molecules after two rounds of replication, if the dispersive model was correct?
3/4 of each DNA molecule would be light and 1/4 would be heavy, leading to a single density.
A new DNA strand can only be synthesized in a ______ to _____ direction. are denoted by numbers (e.g., 3), while others are denoted by numbers with a prime (e.g., 3'). In your answer, make sure to use the correct notation (i.e., 2 is not the same as 2'), otherwise, you will not receive credit.
5' ; 3'
A DNA strand runs 3' to 5'. The complementary strand runs
5' to 3'
A segment of DNA has the sequence 5'-ATGCCC-3'. The complementary sequence would be
5'-GGGCAT-3'
Telomerase uses which of the following as a template?
A short internal RNA
What is a thymine dimer?
A site where two adjacent thymine bases become covalently cross-linked to each other
A __________ __________ is the partial opening of a DNA helix to form two single strands.
Blank 1: replication Blank 2: fork
A phage is a type of____________ that infects____________ cells
Blank 1: virus or viruses Blank 2: bacterial or bacteria
How are the origins of replication adjusted in eukaryotic cells, so that early in the embryonic development of eukaryotic organisms DNA can be replicated faster?
Cells can increase the number of origins used in early development.
Match the types of repair mechanisms with how they work:
Correct Answer -specific >>, target a single kind of lesion in DNA and repair that damage target a single kind of lesion in DNA and repair that damage -nonspecific >>, repair multiple kinds of lesions in DNA, using a single mechanism repair multiple kinds of lesions in DNA, using a single mechanism
The purpose of the Hershey Chase experiments was to determine whether a bacteriophage injected ______ or ______ into bacteria.
DNA protein
The enzyme that relieves DNA supercoiling ahead of the replication fork is
DNA gyrase
Which enzyme covalently links nucleotides together?
DNA polymerase
In their experiments, Avery, MacLeod, and McCarty isolated a substance, which had a transforming activity. Which of the following destroyed that substance's ability to transform bacterial cells?
DNA-digesting enzymes
Which types of cells have more than one origin of replication?
Eukaryotes
In which type of repair mechanism a damaged region of DNA is removed and then replaced by DNA synthesis?
Excision repair
In order for mismatch repair to occur in a bacterial cell, the enzyme machinery must be able to distinguish between the template strand and a newly synthesized strand. How is that achieved?
For a short period of time after replication, the sequence GATC is methylated at the A only on the template strand.
In which of the following chromosomal entities are an individual's traits specified?
Genes
In prokaryotes, the two daughter molecules (each a double strand) produced at the end of replication are intertwined, similar to two links in a chain. What is the name of the enzyme that unlinks the two daughter DNA molecules?
Gyrase
The enzyme _________ uses ATP to unwind the DNA template
Helicase
Which of the following enzymes involved in DNA replication are found at the replication fork in all three types of cells (bacterial, archaeal, and eukaryotic)? Choose all that apply.
Helicase Polymerases Clamp loader Sliding clamp Primase
On this strand, the removal of the last primer leaves a gap that cannot be primed at the ends of the chromosome.
Lagging
Which DNA polymerase acts on the lagging strand to remove primers and replace them with DNA?
I
Which DNA polymerase removes and replaces RNA primer segments in the synthesis of the lagging stand because it has 5' to 3' exonuclease activity.
I
What is the function of the UvrABC complex in excision repair in E. coli?
It binds to the damaged DNA and removes damaged DNA by cleaving a single strand on each side.
In a bacterium, where does termination of replication occur, relative to the origin?
The termination site is opposite to the origin
Which subunit of DNA polymerase III forms the sliding clamp?
The β subunit
Why do eukaryotic cells have multiple origins of replication?
To ensure timely replication of multiple, relatively large chromosomes
What class of enzymes relieve torsional strain in DNA strands ahead of the replication fork?
Topoisomerases
In the Meselson-Stahl experiment, what was the expected composition of DNA molecules after one rounds of replication, if the conservative model was correct?
Two densities should be observed: the DNA strands would be either all-heavy or all-light
The DNA fibers Franklin used in her x-ray diffraction studies came from
Wilkins
Bacterial DNA is typically replicated as
a single replicon
Features of the Watson and Crick model include
a sugar phosphate backbone a double stranded structure a helical structure
The DNA structure proposed by Watson and Crick involves
a sugar phosphate backbone two grooves (major and minor) a helical structure
In a DNA double helix, two hydrogen bonds form between
adenine and thymine
The density of the bacterial DNA following the first round of DNA replication in the Meselson-Stahl experiment can best be described as
an intermediate between 14N and 15N DNA.
The term used to describe two DNA strands that run in opposite directions from each other is
antiparallel
DNA's phosphodiester_________ is composed of sugars and phosphates.
backbone
Viruses that infect bacteria are known as
bacteriophages
Nucleotides contain a sugar, a phosphate, and a nitrogenous
base
In E. coli, oriC is the site at which replication
begins
Telomeres are related to
cellular aging
Genes, which contain trait specifying information, are located on
chromosomes
The two main eukaryotic DNA polymerases that extend DNA are
delta epsilon
The major significance of the Hershey and Chase's experiments is that they
determined that DNA is the genetic material
A heavy isotope of nitrogen was used in the Meselson-Stahl experiment so that
different DNA molecules could be separated via ultracentrifugation.
Franklin used x-ray Blank ___________to suggest that DNA has a helical structure.
diffraction or crystallography
This model of DNA replication suggests that newly synthesized strands of DNA have mixtures of parental and newly synthesized strands of DNA:
dispersive
In order for mismatch repair to occur in a bacterial cell, the enzyme machinery must be able to
distinguish between the template strand and a newly synthesized strand.
RNA polymerases
do not require primers to begin synthesis.
The interaction of two strands of DNA via hydrogen bonds is the
double helix
The level of DNA structure that resembles a spiral staircase is the
double helix
An ______ cuts DNA internally and an ______ cuts at the ends of DNA.
endonuclease; exonuclease
E. coli polymerases I, II, and III have 3' to 5'_______________ activity, which provides them with a proofreading function, i.e. they can remove a mispaired base.
exonuclease
Which of these is not one of the three phases of DNA replication?
extension
A bacteriophage contains (choose all that apply)
genetic material a protein coat
Indicate the 4 nitrogenous bases used in DNA.
guanine cytosine thymine adenine
The enzyme DNA ____________is the topoisomerase involved in DNA replication.
gyrase
List the three phases of DNA replication
initiation termination elongation
A bacterial virus replicates by
introducing its genetic material into the host cell
The primary reason the bacteriophage was an ideal model system for the Hershey Chase experiments was
it is made of only protein and DNA.
An Okazaki fragment is a short fragment of DNA created on the ______ strand of DNA
lagging
During DNA replication, the_________ strand is synthesized continuously while the ________ strand is synthesized as small fragments that are connected to each other to form a continuous strand.
leading lagging
Agents that cause mutation are known as
mutagens
Radiation, UV light, x-rays, and chemicals in the environment can cause mutations in DNA and are therefore referred to as________
mutagens
Select all of the following that are components of a nucleotide.
nitrogenous base phosphate group sugar
Of the following list, which 3 items are required for DNA replication
nucleotides template polymerase
In the 1950s, the British researcher Maurice Wilkins contributed to the discovery of DNA's double helix structure by
producing uniformly oriented DNA fibers
The function of telomeres is to
protect the ends of chromosomes
The results of the Hershey and Chase experiments suggested that DNA was the genetic material because
radioactive bacteriophage DNA was found in the cytoplasm of bacterial cells
The DNA controlled by an origin is called a____________
replicon
When the double stranded DNA helix is unwound, two single strands of DNA are formed. These strands have to be stabilized because their hydrophobic bases are exposed to water. The proteins that stabilize the two single strands are called
single-strand binding proteins
The normal virulent form of Streptococcus pneumoniae is known as the S form because it forms________________ colonies on solid media.
smooth
____________ repair systems target a single kind of lesion in DNA and repair only that damage, while______________ repair systems use a single mechanism to repair multiple kinds of lesions in DNA.
specific nonspecific
List several differences in prokaryotic and eukaryotic replication.
structure of chromosome (linear vs. circular) complexity of enzymology number of origins of replication
The term _____________refers to the coiling of two DNA strands leading to torsional strain.
supercoiling
Chargaff's experiments showed that the amount of adenine in a sample was always the same as the amount of
thymine
The basic design of the Meselson-Stahl experiment is
to label DNA and follow it through 2 rounds of replication.
Griffith performed experiments, which demonstrated
transformation in bacteria.
Which of these are used in RNA?
uracil guanine cytosine adenine
Which E. coli genes encode the proteins required to perform excision repair?
uvrA, uvrB, and uvrC
