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