SmartBook Test 03 Prep

Place the steps of the experiment that Hershey and Chase performed to demonstrate that DNA was the genetic material of bacteriophages in the correct order.

1.) Bacteriophages were grown on media containing radioactive material. 2.)Bacteriophages were allowed to infect bacteria. 3.)A blender was used to remove bacteriophages from cell surfaces. 4.)The sample was centrifuged. 5.)Radioactivity was measured.

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

X-ray diffraction was used to determine that the diameter of a DNA molecule is:

2 nm

Guanine forms _____ hydrogen bonds with cytosine.

3

Guanine forms ________ hydrogen bonds with cytosine.

3

How many hydrogen bonds form between cytosine and guanine in the DNA double helix?

3

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. Some carbons in the structure of nucleotides 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'

By convention, the sequence of DNA bases is usually written in the ______ to _______ direction.

5', 5 prime, five', five prime, 5`, 5′, or 5´ + 3', 3 prime, three', three prime, 3`, 3′, or 3´

A segment of DNA has the sequence 5'-ATGCCC-3'. The complementary sequence would be

5'-GGGCAT-3'

Features of the Watson and Crick model include:

A helical structure A double stranded structure A sugar phosphate backbone

The appearance of colonies of Streptococcus pneumoniae is related to the presence or absence of:

A polysaccharide coat

A bacteriophage contains (choose all that apply):

A protein coat Genetic material

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

Indicate the 4 nitrogenous bases used in DNA.

Adenine Guanine Cytosine Thymine

Which of these are used in RNA?

Adenine Guanine Cytosine Uracil

In a DNA double helix, two hydrogen bonds form between:

Adenine and thymine

DNA's phosphodiester ______ is composed of sugars and phosphates.

Backbone or Spine

Viruses that infect bacteria are known as:

Bacteriophages

Nucleotides contain a sugar, a phosphate, and a nitrogenous_______.

Base

Why do we say that a DNA or RNA strand has an intrinsic polarity?

Because it has a free 5' phosphate at one end and a free 3' OH group at the other end

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.

PCNAThe function of telomeres is to

Select all of the following that are components of a nucleotide.:

Phosphate group Sugar Nitrogenous base

The DNA backbone is composed of (choose all that apply)

Phosphate groups. Sugars.

Repeating sugar and phosphate units in a single DNA strand make up the:

Phosphodiester backbone.

Adjacent nucleotides in the same DNA strand are held together by covalent bonds known as _______ bonds.

Phosphodiester or Phosphoester

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

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 purpose of the Hershey Chase experiments was to determine whether a bacteriophage injected ______ or ______ into bacteria.

Protein DNA

In the Hershey Chase experiments, the isotope 35S was used to label _______ and the isotope 32P was used to label ______.

Proteins, DNA

Which enzymes did Avery, MacLeod, and McCarty use in order to identify the genetic material?

RNA digesting enzymes Protein digesting enzymes DNA digesting enzymes

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

Order the steps in excision repair from first to last, starting at the top.

Recognition, Removal, Resynthesis

A _____ ______ is the partial opening of a DNA helix to form two single strands.

Replication Fork

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.

Sliding clamp Clamp loader Helicase Polymerases Primase

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 Non-specific

The two general categories of DNA repair are

Specific Nonspecific

List several differences in prokaryotic and eukaryotic replication.

Structure of chromosome (linear vs. circular) Number of origins of replication Complexity of enzymology

Because of alternating double and single bonds in nitrogenous bases in nucleic acids, they exist as two different structural forms in solution. The different structural forms are called ________.

Tautomers

Because of alternating double and single bonds in nitrogenous bases in nucleic acids, they exist as two different structural forms in solution. The different structural forms are called:

Tautomers

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 molecul

Telomerase

Which enzyme prevents chromosomal shortening by attaching a repeat sequence to the ends of chromosomes?

Telomerase

Short, repeated sequences of DNA are characteristic of

Telomeres

What is the name of the regions at the ends of eukaryotic chromosomes?

Telomeres

______ are short protective repeats of DNA on the ends on eukaryotic chromosomes which are generated by the enzyme ________.

Telomeres, Telomerase

Griffith's experiments were important because they showed:

That the genetic material could be passed from one cell to another

Which end of a complementary DNA strand base paired with the strand shown in this figure would be at the top?

The 3' end

During the synthesis of the new DNA molecule, where are the new nucleotides added by DNA polymerase?

The 3' end of the growing strand

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

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 partial opening of a DNA helix to form two single strands is called

The replication fork

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

Chargaff's rule indicates that the amount of A in a sample is equal to 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

Consider a double stranded DNA molecule. In complementary base pairing, A pairs with _____ and C pairs with ______

Thymine, Guanine

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

Griffith performed experiments, which demonstrated:

Transformation in bacteria.

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 structure proposed by Watson and Crick involves:

Two grooves (major and minor) A helical structure A sugar phosphate backbone

Helicase, Gyrase, Primase, Polymerase

Unwinds, Relieves, Makes, Attaches

A phage is a type of _____ that infects _____ cells.

Virus, Bacteria

A heavy isotope of nitrogen was used in the Meselson-Stahl experiment so that

different DNA molecules could be separated via ultracentrifugation.

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

Radiation, UV light, x-rays, and chemicals in the environment can cause mutations in DNA and are therefore referred to as

mutagens

Of the following list, which 3 items are required for DNA replication

nucleotides polymerase template

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

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

All DNA polymerases require a short strand of DNA or RNA, called a______ , to begin their synthesis

primer

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 DNA controlled by an origin is called a

replicon

DNA replication that leads to the production of double helices with one parental strand and one newly synthesized strand is consistent with

semiconservative 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 term ____ refers to the coiling of two DNA strands leading to torsional strain.

supercoiling

leading

synthesized continuously

DNA replication in E. coli ends at a site called the

terminus

If normal fibroblast cells are grown in cell culture and the enzyme telomerase is introduced in them:

the cells show an increased lifespan

DNA repair mechanisms have likely evolved because

there is no way for cells to avoid exposure to mutagens

The basic design of the Meselson-Stahl experiment is

to label DNA and follow it through 2 rounds of replication.

Which E. coli genes encode the proteins required to perform excision repair?

uvrA, uvrB, and uvrC

Bacterial replication (for example in E. coli) begins at

a single origin

Bacterial DNA is typically replicated as

a single replicon

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

In E. coli, oriC is the site at which replication

begins

Telomeres are related to

cellular aging

The enzyme _______ is the topoisomerase involved in DNA replication.

gyrase

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

List the three phases of DNA replication:

initiation termination elongation

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.

Genes, which contain trait specifying information, are located on:

Chromosomes

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

Choose all characteristics of the transforming substance isolated by Avery, MacLeod and McCarty.:

DNA-digesting enzymes destroyed its transforming ability. The elemental composition of the substance was very similar to that of DNA. Protein-digesting enzymes did not affect its transforming ability. RNA-digesting enzymes did not affect its transforming ability.

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

Different models for DNA replication include:

Dispersive replication Conservative replication Semiconservative replication

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 part of the Watson-Crick model?

Each DNA molecule is composed of 2 phosphodiester strands. Each DNA molecule is composed of two strands that run antiparallel.

Cells have several non-specific repair pathways. Indicate which of the following are two general categories of repair mechanisms:

Error-free Error-prone

The model organism used by Meselson and Stahl was

Escherichia coli.

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

In the Meselson-Stahl experiment, what was the expected composition of DNA molecules after two rounds of replication, if the semiconservative model was correct?

Half of the molecules would have 2 light strands and half would have a heavy and light strand.

The enzyme ______ uses ATP to unwind the DNA template.

Helicase

The experiments with radioactively labeled phage that showed that DNA was the genetic material were performed by:

Hershey and Chase

In DNA, the two tautomers in the bases exhibit differences in what type of bonding pattern?

Hydrogen

These individual bonds are low-energy, but together they are strong enough to hold the two strands of a double-stranded DNA molecule together.

Hydrogen bonds between basepairs

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

Which DNA polymerase does not seem to play a role in replication but is involved in the DNA repair process?

II

A bacterial virus replicates by:

Introducing its genetic material into the host cell

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.

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

On this strand, the removal of the last primer leaves a gap that cannot be primed at the ends of the chromosome.

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

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 of RNA complementary to the DNA. Makes a primer about 10 -20 nucleotides in length.

______ 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

Agents that cause mutation are known as

Mutagens

Which of these is not required for DNA replication?

NADPH

Meselson and Stahl used two isotopes of ________ in their DNA replication experiments so that the daughter strands could be distinguished from the parental strands.

Nitrogen

Short fragments of DNA created on the lagging strand of DNA during replication are called

Okazaki fragments

The DNA fibers Franklin used in her x-ray diffraction studies came from:

Wilkins

Franklin determined that the structure of DNA was helical based on:

X-ray diffraction analysis

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.

An ______ cuts DNA internally and an ______ cuts at the ends of DNA.

endonuclease; exonuclease

In E. coli, the SOS response is part of the

error-prone repair mechanism

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

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