Chapter 15 - DNA and the Gene Practice Quiz
Put the following steps of DNA replication in chronological order. 1. Single-stranded binding proteins attach to DNA strands. 2. Hydrogen bonds between base pairs of antiparallel strands are broken 3. Primase binds to the site of origin 4. DNA polymerase binds to the template strand 5. An RNA primer is created
2, 1, 3, 5, 4
In an analysis of the nucleotide composition of DNA, which of the following will be found?
A + C = G + T
For a science fair project, two students decided to repeat the Hershey and Chase experiment, with modifications. They decided to label the nitrogen of the DNA, rather than the phosphate. They reasoned that each nucleotide has only one phosphate and two to five nitrogens. Thus, labeling the nitrogens would provide a stronger signal than labeling the phosphates. Why won't this experiment work?
Amino acids (and thus proteins) also have nitrogen atoms; thus, the radioactivity would not distinguish between DNA and proteins.
A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in 15N medium for several generations and then transfer them to 14N medium. Which pattern in Figure 16.1 would you expect if the DNA was replicated in a conservative manner?
B- w/ ring in the bottom and top
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.
Suppose you are provided with an actively dividing culture of E. coli bacteria to which radioactive thymine has been added. What would happen if a cell replicates once in the presence of this radioactive base?
DNA in both daughter cells would be radioactive.
Which enzyme catalyzes the elongation of a DNA strand in the 5' --> 3' direction?
DNA polymerase III
A new DNA strand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end.
Which of the following statements describes the eukaryotic chromosome?
It consists of a single linear molecule of double-stranded DNA.
What is the role of DNA ligase in the elongation of the lagging strand during DNA replication?
It joins Okazaki fragments together.
Who performed classic experiments that supported the semiconservative model of DNA replication?
Meselson and Stahl
What determines the nucleotide sequence of the newly synthesized strand during DNA replication?
The nucleotide sequence of the template strand.
Researchers found E. coli that had mutation rates 100 times higher than normal. Which of the following is the most likely cause of these results?
The proofreading mechanism of DNA polymerase was not working properly.
In an experiment, DNA is allowed to replicate in an environment with all necessary enzymes, dATP, dCTP, dGTP, and radioactively labeled dTTP (3H thymidine) for several minutes and then switched to nonradioactive medium. It is then viewed by electron microscopy and autoradiography. The drawing below represents the results. Grains represent radioactive material within the replicating eye. Which is the most likely interpretation?
There are two replication forks going in opposite directions.
To repair a thymine dimer by nucleotide excision repair, in which order do the necessary enzymes act?
endonuclease, DNA polymerase I, DNA ligase
Which of the following separates the DNA strands during replication?
helicase
You briefly expose bacteria undergoing DNA replication to radioactively labeled nucleotides. When you centrifuge the DNA isolated from the bacteria, the DNA separates into two classes. One class of labeled DNA includes very large molecules (thousands or even millions of nucleotides long), and the other includes short stretches of DNA (several hundred to a few thousand nucleotides in length). These two classes of DNA probably represent
leading strands and Okazaki fragments.
Which of the following covalently connects segments of DNA?
ligase
Semiconservative replication involves a template. What is the template?
one strand of the DNA molecule
Which of the following synthesizes short segments of RNA?
primase
What is the function of topoisomerase?
relieving strain in the DNA ahead of the replication fork
DNA is synthesized through a process known as ________.
semiconservative replication
Which of the following help(s) to hold the DNA strands apart while they are being replicated?
single-strand DNA binding proteins
What is a telomere?
the ends of linear chromosomes
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 determines the nucleotide sequence of the newly synthesized strand during DNA replication?
the nucleotide sequence of the template strand
Mendel and Morgan did not know about the structure of DNA; however, which of the following of their contributions was (were) necessary to Watson and Crick?
the particulate nature of the hereditary material
In humans, xeroderma pigmentosum (XP) is a disorder of the nucleotide excision repair mechanism. These individuals are unable to repair DNA damage caused by ultraviolet light. Which of the following are the most prominent types of DNA lesions in individuals suffering from xeroderma pigmentosum?
thymine dimers
What is the function of DNA polymerase III?
to add nucleotides to the end of a growing DNA strand
