Chapter 14: DNA: The Genetic Material

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

proteins ; DNA

Topoisomerase

relieves coiling in DNA strands ahead of the replication fork

nonspecific repair mechanism

repair multiple kinds of lesions in DNA, using a single mechanism

A ____ _____ is the partial opening of a DNA helix to form two single stands.

replication fork

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

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

Where are the enzymes in the replisome active on?

the leading and the lagging strands

DNA repair mechanisms have evolved because

there is no way for cells to avoid exposure to mutagens

Guanine forms _____ hydrogen bonds with cytosine.

three

Griffith performed experiments, which demonstrated

transformation in bacteria

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

uvrA, uvrB, and uvrC

Phages are a type of _____ that infect ____ cells.

virus ; bacteria

Franklin determined that the structure of DNA was helical based on

x-ray diffraction analysis

The problems in replicating the ends of linear chromosomes are caused by what?

- the directionality of polymerases - the need for a primer

A new DNA strand can only be synthesized in a ___ to ___ direction.

5' ; 3'

What is a thymine dimer?

A site where two adjacent thymine bases become covalently cross-linked to each other

Function of DNA polymerase in E coli? I

Acts on the lagging strand to remove primers and replace them with DNA

The density of the bacterial DNA following the first round of DNA replication in the Meselson-Stahl experiment can be best described as:

An intermediate between 14N and 15N DNA.

Polymerase

Attaches a nucleotide to the 3' end of the DNA strand

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

What are telomeres related to?

Cellular aging

Which types of cells have more than one origin of replication?

eukaryotes

E. coli polymerases I, II, III have 3' to 5' _____ activity, which provides them with a proofreading function, i.e. they can remove a mispaired base.

exonuclease

Bacterial DNA is typically replicated as

a single replicon

The ends of the chromosomes shorten when telomerase is

absent

What is the term used to describe two DNA strands that run in opposite direction from each other?

antiparallel

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

backbone

Telomeres are related to

cellular aging

Genes which contain the information to specify traits are located on

chromosomes

The major significance of the Hershey and Chase's experiments is that they

determined that DNA is the genetic material

Which type of Streptococcus pneumoniae would lead to death if injected into a mouse?

live smooth

In an aging cell, the activity of telomerase would be

low

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

mutagens

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

Function of DNA polymerase in E coli? II

not involved in replication but used for DNA repair

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

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

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 DNA, 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

In the 1950s, the British researcher Maurice Wilkins contributed to the discovery of DNA's double helix structure by

producing the first true crystals of DNA molecules

Chromosomes are composed of DNA and _____.

protein

Features of the Watson and Crick model include what?

- A double stranded structure - A helical structure - A sugar phosphate backbone

What is part of the Watson-Crick model?

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

What does DNA primase do?

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

In order to purify the genetic material, Avery, MacLeod, and McCarty used which enzymes in their experiments?

- Protein digesting enzymes - DNA digesting enzymes - RNA digesting enzymes

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

- error-prone -error-free

What does a bacteriophage contain?

- genetic material - a protein coat

What does DNA primase do?

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

What enzymes are involved in DNA replication that are found at the replication fork in all three types of cells (bacterial, archaeal, and eukaryotic)?

-clamp loader -sliding clamp -two polymerases -helicase -primase

Different models for DNA replication include:

-conservative replication -dispersive replication -semiconservative replication

What types of Streptococcus pneumoniae bacteria did Griffith inject into mice?

-rough -heat killed -smooth -live

Steps of the experiment that Hershey and Chase performed to demonstrate that DNA was the genetic material of bacteriophages

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.

The two main eukaryotic DNA polymerases that extend DNA are

1. Epsilon 2. Delta

What are the three phases of DNA replication?

1. Initiation 2. Elongation 3. Termination

What are the components of a nucleotide?

1. Nitrogenous base 2. Sugar 3. Phosphate group

Steps in excision repair

1. Recognition of damage 2. Removal of the damaged region 3. Resynthesis using the information on the undamaged strand as a template

List several differences in prokaryotic and eukaryotic replication.

1. Structure of chromosome (linear vs. circular) 2. number of origins of replication 3. complexity of enzymology

What are the steps of lagging strand synthesis?

1. Synthesize primers using primase 2. Synthesize DNA 3. Replace RNA primers with DNA 4. Seal nicks in the DNA

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

DNA ; protein

What 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 destroyed that substances ability to transform bacterial cells?

DNA-digesting enzymes

This model of DNA replication suggests that newly synthesized strands of DNA have mixtures of parental and newly synthesized strands of DNA

Dispersive

What is the interaction of two strands of DNA via hydrogen bonds?

Double helix

In which type of repair mechanism a damaged region of DNA is removed and then replaced by DNA synthesis?

Excision repair

In cancer cells as compared to normal cells, telomerase is present in what sort of levels?

Higher

Which DNA polymerase removes and replaces DNA primer segments in the synthesis of the lagging strand because it has 5' to 3' exonuclease activity.

I

DNA replication in eukaryotic cells is complicated by

Linear chromosomes

The experiments used to distinguish between the three potential DNA replication mechanisms were performed by ________.

Meselson and Stahl

What is not required for DNA replication?

NADPH

1'

Nitrogenous base

3'

OH group

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

Okazaki fragments

5'

Phosphate group

Leading strand

Synthesized continuously

Primase

Synthesizes RNA primers. Makes a 10-12 bp complementary primer to the DNA

Charfaff'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 _____.

T ; G

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

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

Telomeres ; Telomerase

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

The 3' end of the growing strand

Function of DNA polymerase in E coli? III

The main replication enzyme

In the bacterium, where does termination of replication occur, relative to the origin?

The termination site is opposite to the origin

How many hydrogen bonds are formed between adenine and thymine in the double DNA helix?

Two

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.

Helicase

Unwinds the double helix. Causes DNA strand separation at the origin of replication

What is used in RNA?

guanine uracil cytosine adenine

The enzyme DNA ____ is the topoisomerase involved in DNA replication.

gyrase

The enzyme _______ uses ATP to unwind the DNA template.

helicase

What does the sliding clamp of a DNA polymerase do?

holds the polymerase to the DNA template

An Okazaki fragment is a short fragment of DNA created on the _____ strand of DNA.

lagging

The normal virulent form of Streptococcus pneumonia is known as the S form because it forms _____ colonies on solid media.

smooth

The term _____ refers to the coiling of two DNA stands leading to torsional stain.

supercoiling

Lagging strand

synthesized in small fragments that are later connected

specific repair mechanism

target a single kind of lesion in DNA and repair that damage

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 molecule.

telomerase