bio ch 14
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
Which enzymes did Avery, MacLeod, and McCarty use in order to identify the genetic material?
DNA digesting enzymes RNA digesting enzymes protein digesting enzymes
The enzyme that relieves DNA supercoiling ahead of the replication fork is
DNA gyrase
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 type of repair mechanisms 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
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
Telomeres are related to
cellular aging
The enzyme _____ uses ATP to unwind the DNA template.
helicase
The primary purpose of the Meselson and Stahl experiments was to determine
how DNA replicates.
In an aging cell, the activity of telomerase would be
low
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 undamaged strand as a template
The experiments used to distinguish between the three potential DNA replication mechanisms were performed by
Meselson and Stahl
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
Chargaff's experiments showed that the amount of adenine in a sample was always the same as the amount of
thymine
Chargaff's rule indicates that the amount of A in a sample is equal to the amount of _____ and the amount of C in a sample is equal to the amount of ______.
thymine; guanine
Griffith performed experiments, which demonstrated
transformation in bacteria.
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
Which model for DNA replication suggests that both strands of the double helix remain intact and the new DNA double helix consists of two new DNA strands?
The conservative model
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
This type of primase is a combination of RNA polymerase and DNA polymerase that makes short RNA primers and then extends them with DNA to produce the final primer:
eukaryotic
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.
sugar phosphate group nitrogenous base
______ are short protective repeats of DNA on the ends on eukaryotic chromosomes which are generated by the enzyme _______
telomeres; telomerase
List the three phases of DNA replication:
termination elongation initiation
Griffith's experiments were important because they showed
that the genetic material could be passed from one cell to another
Agents that cause mutation are known as
mutagens
Genes, which contain trait specifying information, are located on
chromosomes
How many hydrogen bonds are formed between adenine and thymine in the double DNA helix?
2
X-ray diffraction was used to determine that the diameter of a DNA molecule is
2 nm
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
Which types of cells have more than one origin of replication?
Eukaryotes
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.
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 Clamp loader Polymerases Sliding clamp Primase
Which enzyme prevents chromosomal shortening by attaching a repeat sequence to the ends of chromosomes?
Telomerase
Choose all characteristics of the transforming substance isolated by Avery, MacLeod and McCarty.
--DNA-digesting enzymes destroyed its transforming ability. --RNA-digesting enzymes did not affect its transforming ability. --Protein-digesting enzymes did not affect its transforming ability. --The elemental composition of the substance was very similar to that of DNA.
A phage is a type of _______ that infects ______ cells.
virus; bacterial
Franklin determined that the structure of DNA was helical based on
x-ray diffraction analysis
Bacterial replication (for example in E. coli) begins at
a single origin
Place the steps of lagging strand synthesis in the correct order (start at the top):
1. synthesize primers using primase 2. synthesize DNA 3. replace RNA primers with DNA 4. seal nicks in the DNA
Which enzyme covalently links nucleotides together?
DNA polymerase
Which of the following facilitates the reversal of damage to our hereditary material before a permanent mutation can occur?
DNA repair systems
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
The experiments with radioactively labeled phage that showed that DNA was the genetic material were performed by
Hershey and Chase
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.
On this strand, the removal of the last primer leaves a gap that cannot be primed at the ends of the chromosome.
Lagging
Why do eukaryotic cells have multiple origins of replication?
To ensure timely replication of multiple, relatively large chromosomes
Features of the Watson and Crick model include
a double stranded structure a helical structure a sugar phosphate backbone
Bacterial DNA is typically replicated as
a single replicon
Indicate the 4 nitrogenous bases used in DNA.
adenine cytosine thymine guanine
Viruses that infect bacteria are known as
bacteriophages
Nucleotides contain a sugar, a phosphate, and a nitrogenous
base
An ______ cuts DNA internally and an ______ cuts at the ends of DNA.
endonuclease; exonuclease
the amount of guanine always equals the amount of ________
cytosine
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
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.
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
Which of these are used in RNA?
guanine cytosine uracil adenine
Match these enzymes involved in DNA replication with their function.
helicase- unwinds the double helix gyrase-relieves coiling in DNA strands ahead of the replication fork primase- makes a 10-12 bp complementary primer to the DNA polymerase- attaches a nucleotide to the 3' end of the DNA strand
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
As the lagging strand is being synthesized, adjacent Okazaki fragments are joined by the enzyme DNA
ligase
The level of telomerase stays high in ______, despite their age.
lymphocytes
DNA primase (choose all that apply)
makes a primer about 10 -20 nucleotides in length. makes a primer of RNA complementary to the DNA.
_____ repair is responsible for removing bases that were incorrectly incorporated into DNA during replication.
mismatch
During semiconservative DNA replication
one of the strands in each new double helix comes from the original molecule, and one is newly synthesized
The DNA backbone is composed of (choose all that apply)
phosphate groups. sugars.
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
In DNA, consecutive nucleotides are linked via ______ bonds, which are made between the 5' phosphate of one nucleotide and the 3' ______ group of another nucleotide.
phosphodiester; hydroxyl or OH
Damage caused by UV light leading to thymine dimers is corrected during photorepair by the enzyme ______.
photolyase
The enzyme DNA ______ covalently links nucleotides to synthesize new DNA strands together during DNA replication.
polymerase
Of the following list, which 3 items are required for DNA replication
polymerase template nucleotides
The enzyme DNA ______ synthesizes the RNA primers required by DNA polymerases during replication.
primase
In the replisome, the _____ is composed of primase, helicase, and accessory proteins that prime the lagging strand.
primosome
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
A ______ ______ is the partial opening of a DNA helix to form two single strands.
replication fork
DNA replication that leads to the production of double helices with one parental strand and one newly synthesized strand is consistent with
semiconservative replication
Different models for DNA replication include:
semiconservative replication dispersive replication conservative replication
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 two general categories of DNA repair are
specific nonspecific
Match the types of repair mechanisms with how they work:
specific- target a single kind of lesion in DNA and repair that damage nonspecific- repair multiple kinds of lesions in DNA, using a single mechanism
List several differences in prokaryotic and eukaryotic replication.
structure of chromosome (linear vs. circular) number of origins of replication complexity of enzymology
DNA replication in eukaryotic cells is complicated by the fact that eukaryotic cells have
the larger amount of DNA organized into multiple chromosomes, and the linear structure of the chromosomes.
The enzymes in the replisome are active on
the leading and the lagging strands
The problems in replicating the ends of linear chromosomes are caused by (choose all that apply)
the need for a primer the directionality of polymerases
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
The DNA structure proposed by Watson and Crick involves
two grooves (major and minor) a helical structure a sugar phosphate backbone
