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