DNA Replication
Different models for DNA replication include:
semiconservative replication, conservative replication, dispersive replication
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
The basic design of the Meselson-Stahl experiment is
to label DNA and follow it through 2 rounds of replication.
As the lagging strand is being synthesized, adjacent Okazaki fragments are joined by the enzyme DNA ___________.
Ligase
The experiments used to distinguish between the three potential DNA replication mechanisms were performed by
Meselson and Stahl.
Which of these is not required for DNA replication?
NADPH
The enzyme DNA _________ synthesizes the RNA primers required by DNA polymerases during replication.
Primase
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
Bacterial DNA is typically replicated as
a single replicon
Telomeres are related to
cellular aging
The amount of the enzyme _______ declines within cells as they age.
Telomerase
An ______ cuts DNA internally and an ______ cuts at the ends of DNA.
endonucleases; exonucleases
During semiconservative DNA replication
one of the strands in each new double helix comes from the original molecule, and one is newly synthesized.
Which of the following are short repeats of DNA on the ends of eukaryotic chromosomes?
Telomeres
Bacterial replication (for example in E. coli) begins at
a single origin
The primary purpose of the Meselson and Stahl experiments was to determine
how DNA replicates.
As the lagging strand is being synthesized, adjacent Okazaki fragments are joined by the enzyme DNA _________.
ligase
In an aging cell, the activity of telomerase would be
low
The enzyme DNA ___________ covalently links nucleotides to synthesize new DNA strands together during DNA replication.
polymerase
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
What is the name of the regions at the ends of eukaryotic chromosomes?
telomeres
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
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
DNA replication in eukaryotic cells is complicated by the fact that eukaryotic cells have
Linear chromosomes
The level of telomerase stays high in ______, despite their age.
Lymphocytes
Which enzyme prevents chromosomal shortening by attaching a repeat sequence to the ends of chromosomes?
Telomerase
Of the following list, which 3 items are required for DNA replication
nucleotides, template, polymerase
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
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
_______________ are short protective repeats of DNA on the ends on eukaryotic chromosomes which are generated by the enzyme _______________.
telomeres, telomerase
DNA primase (choose all that apply)
-makes a primer about 10 -20 nucleotides in length. -makes a primer of RNA complementary to the DNA.
On this strand, the removal of the last primer leaves a gap that cannot be primed at the ends of the chromosome.
Lagging
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
Which types of cells have more than one origin of replication?
Eukaryotes
In order to determine the density of DNA strands, Meselson and Stahl used this technique so that DNA fragments would migrate to the area in the gradient where they had the same density.
A cesium chloride gradient
Telomerase uses which of the following as a template?
A short internal RNA
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.
Clamp loader Primase Helicase Sliding clamp Polymerases
The enzyme that relieves DNA supercoiling ahead of the replication fork is
DNA gyrase
Which enzyme covalently links nucleotides together?
DNA polymerase
The two main eukaryotic DNA polymerases that extend DNA are
Delta, Epsilon
The model organism used by Meselson and Stahl was
Escherichia coli.
Based on replication proteins, DNA replication in archaea is most similar to that of
Eukaryotes
The enzyme _________ uses ATP to unwind the DNA template.
Helicase
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
List the three phases of DNA replication:
Initiation, elogation, and termination
Why do eukaryotic cells have multiple origins of replication?
To ensure timely replication of multiple, relatively large chromosomes
List several differences in prokaryotic and eukaryotic replication.
complexity of enzymology structure of chromosome (linear vs. circular) number of origins of replication
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
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 (SSB)
Match the following strands with the type of synthesis. Leading Strand Lagging Strand
-Synthesized continuously -Synthesized in small fragments that are later connected
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
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 of these is not one of the three phases of DNA replication?
extension
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