Module 5 Study

What is the function of topoisomerase?

relieving strain in the DNA ahead of the replication fork

An Okazaki fragment has which of the following arrangements?

5' RNA nucleotides, DNA nucleotides 3'

At a specific area of a chromosome, the following sequence of nucleotides 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 (T) of the template. Which of the following represents the primer sequence?

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

Why is it so important to be able to amplify DNA fragments when studying genes?

A gene may represent only a millionth of the cell's DNA.

During DNA replication, which of the following enzymes removes the RNA nucleotides from the primer and adds equivalent DNA nucleotides to the 3' end of Okazaki fragments?

DNA polymerase I

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

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

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

Erwin Chargaff

Why do histones bind tightly to DNA?

Histones are positively charged, and DNA is negatively charged.

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

It joins Okazaki fragments together.

In his transformation experiments, what did Griffith 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.

What is meant by the description "antiparallel" regarding the two strands of nucleic acids that make up DNA?

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

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.

How is transformation in bacteria most accurately described?

assimilation of external DNA into a cell

The elongation of the leading strand during DNA synthesis

depends on the action of DNA polymerase.

During DNA replication, which of the following enzymes separates the DNA strands during replication?

helicase

In a nucleosome, the DNA is wrapped around

histones

Which of the following modifications is most likely to alter the rate at which a DNA fragment moves through a gel during electrophoresis?

increasing the length of the DNA fragment

During DNA replication, which of the following enzymes covalently connects segments of DNA?

ligase

The leading and the lagging strands of DNA formed during DNA replication 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.

It became apparent to Watson and Crick after completion of their model that the DNA molecule could carry a vast amount of hereditary information based on which of the following characteristics?

the sequence of bases