Biology Chapter 16

In E. coli, there is a mutation in a gene called dnaB that alters the helicase that normally acts at the origin Which of the following would expect as a result of the mutation?

No replication fork will be formed.

If a cell were unable to produce histone proteins, which of the following would be a likely effect?

The cell's DNA couldn't be packed into its nucleus.

To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?

endonuclease, DNA polymerase I, DNA ligase

What is the function of topoismerase?

relieving strain in the DNA ahead of the replication fork

At a specific area of a chromosome, the sequence of nucleotides below is present where the chain opens to form a replication fork: 3' C C T A G G C T G C A A T C C 5' An RNA primer is formed starting at the underlined T of the template. Which of the following represents the primer sequence?

5' A C G U U A G G 3'

Cytosine makes up 42% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?

8%

In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy" nitrogen (15N) and then transferred them to a medium containing 14N. Which of the results in the figure above would be expected after one round of DNA replication in the presence of 14N?

D

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

DNA polymerase III

What is the basis for the difference in how the leading and lagging strands of DNA molecules are synthesized?

DNA polymerase can join new nucleotides only to the 3' end of a growing strand.

A new DNA strand elongates only in the 5' 3' direction because

DNA polymerase can only add nucleotides to the free 3' end.

After mixing a heat-killed, phosphorescent strain of bacteria with a living nonphosphorescent strain, you discover that some of the living cells are now phosphorescent. Which observations would provide the best evidence that the ability to fluoresce is a heritable trait?

Descendants of the living cells are also phosphorescent.

Why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged.

Which of the enzymes separates the DNA strands during replication?

I

Which of the enzymes covalently connects segments of DNA?

III

Which of the enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

IV

Which of the following statements describes the eukaryotic chromosome?

It consists of a single linear molecule of double-stranded DNA plus proteins.

What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?

It joins Okazaki fragments together.

Replications in prokaryotes differs from replication in eukaryotes for which of the following reasons?

Prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many.

What is meant by the description "antiparallel" regarding the strands that make up DNA?

The 5' to 3' direction of one strand runs counter to the 5' 3' direction of the other strand.

Which of the enzymes synthesizes short segments of RNA?

V

Which of the following would you expect of a eukaryote lacking telomerase?

a reduction in chromosome length in gametes

The enzyme telomerase solves the problem of replication at the ends of linear chromosomes by which method?

adding numerous short DNA sequences such as TTAGGG, which form a hairpin turn

How do we describe transformation in bacteria?

assimilation of external DNA into a cell

In a nucleosome, the DNA is wrapped around

histones.

The spontaneous loss of amino groups from adenine in DNA results in hypoxanthine, an uncommon base, opposite thymine. What combination of proteins could repair such damage?

nuclease, DNA polymerase, DNA ligase

Which of the following represents the order of increasingly higher levels of organization of chromatin?

nucleosome, 30-nm chromatin fiber, looped domain

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

single-strand binding proteins

In his work with pneumonia-causing bacteria and mice, Griffith found that

some substance from pathogenic cells was transferred to nonpathogenic cells, making them pathogenic.

The DNA of telomeres has been found to be highly conserved throughout the evolution of eukaryotes. What does this most probably reflect?

that the critical function of telomeres must be maintained

The leading and the lagging strands differ in that

the leading strand is synthesized in the same direction as the movement of the replication fork, and the lagging strand is synthesized in the opposite direction.

What is the function of DNA polymerase III?

to add nucleotides to the 3' end of a growing DNA strand

An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

In an analysis of the nucleotide composition of DNA, which of the following will be found?

A + C = G + T

In trying to determine whether DNA or protein is the genetic material, Hershey and Chase made use of which of the following facts?

DNA contains phosphorus, whereas protein does not.

Which of the following investigators was/were responsible for the following discovery? In DNA from any species, the amount of adenine equals the amount of thymine, and the amount of guanine equals the amount of cytosine.

Erwin Chargaff

In his transformations experiments, what did Giffith observe?

Mixing a heat-killed pathogenic strain of bacteria with a living nonpathogenic strain can convert some of the living cells into the pathogenic form.