BIO 150 Chapter 16

How many replication forks are produced when DNA denatures at an origin?

2

Which of the following is correct?

A forms 2 hydrogen bonds with T; G forms 3 hydrogen bonds with C

What is a replication bubble?

A locally denatured segment of DNA where replication originates

In an analysis of the nucleotide composition of DNA to see which bases are equivalent in concentration, which of the following would be TRUE?

A+C=G+T

Where does the initiator protein bind DNA at the start of replication?

At an origin of replication

If cytosine makes up 22% of the nucleotides in a sample of DNA from an organism, then adenine would make up what percent of the bases?

28

During replication, the direction of synthesis of new DNA from the leading and lagging strands is

5′ to 3′ only.

Which of the following descriptions best fits the class of molecules known as nucleotides?

a nitrogen base, a phosphate group, and a five-carbon sugar

In both prokaryotes and eukaryotes, DNA replication is

bidirectional and semiconservative.

Damaged DNA is excised and repaired by

both DNA polymerase I and ligase

In Griffith's experiments, a harmless variant of S. pneumoniae became pathogenic when mixed with a heat-killed pathogenic variant as a result of

transformation

If radioactive phosphorus (32p) is used in the culture medium of bacteria that harbor phage viruses, it will later appear in the

viral DNA

If radioactive sulfur (35S) is used in the culture medium of bacteria that harbor phage viruses, it will later appear in the

viral coats

After removal of the RNA primers and replacement with DNA nucleotides, the single-stranded nick adjacent to Okazaki fragments is filled in through a reaction that involves which enzyme?

DNA ligase

After a region of DNA has been replicated, ______ removes the RNA primers.

DNA polymerase I

Which enzyme catalyzes the elongation of a DNA strand in the 5'- 3' direction?

DNA polymerase III

Which enzyme elongates the new DNA strand starting at an RNA primer?

DNA polymerase III

What allows for the base-pairing error rate to be kept very low during replication?

DNA repair mechanisms can fix the mispaired bases.

Which enzyme activity is associated with DNA polymerase I?

E. All of the above

As helicase unwinds the DNA molecule, what keeps the strands apart?

Single-strand binding proteins

Which of the following are necessary for DNA replication?

Template DNA, DNA polymerases and four dNTPs (nucleotides)

DNA replication is said to be semiconservative. This means that

each new double helix consists of 1 old and 1 new strand

Telomeres

get shorter with continued cell division.

After the formation of replication bubbles, which of the following is the correct sequence of enzyme use for the synthesis of the lagging DNA strand?

helicases, primase, DNA polymerase III, DNA polymerase I, ligase

The new DNA strand being produced in the 5' to 3' direction is called the _____ strand.

leading

The two strands of a DNA double helix are antiparallel. This means that

one strand runs in the 5'Æ3' direction and the other runs in the 3' Æ5' direction.

Which of the following is LEAST related to the others in the list?

promoter

Which of the following help to hold the DNA strands apart while they are being replicated?

single-stranded binding proteins

When a double-stranded DNA molecule is heated, it denatures into two single-stranded molecules. The reason for this is that

the heat breaks the hydrogen bonds holding the bases together in the center of the molecule but does not affect the covalent bonds of the backbone.

Scientists have discovered how to put together a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have

the protein and DNA of T4

Chargaff found that for DNA

the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1

The two most basic steps of DNA replication are

the template strands are denatured (separated ) and a new strand is synthesized

What is the function of DNA polymerase III in E. coli?

to add nucleotides to the end of a growing DNA strand

Which of the following is not true of DNA?

Each turn of the double helix is 4.3 nm long

. The X-ray diffraction studies conducted by ______ were key to the discovery of the structure of DNA.

Franklin

DNA ligase functions in the

B. elongation of the lagging strand by joining Okazaki fragments C. DNA repair Both B and C are correct

What is the primer that is required to initiate the synthesis of a new DNA strand?

a small piece of RNA

is the fixing of mistakes made during DNA replication; ______ is the fixing of damage to a pre-existing double helix.

Mismatch repair . . . excision repair

The problem of replicating the lagging strand--that is, adding bases in the 3'- 5' direction--is solved by making

Okazaki fragments

Which of the following statements does NOT apply to the Watson and Crick model of DNA?

The two strands of the helix are held together by covalent bonds.

Which kind of enzyme prevents DNA from supercoiling replication fork migrates during replication?

Topoisomerase (gyrase)