AP Bio Ch. 16.2
DNA replication is said to be semiconservative. This means that _____.
each new double helix consists of one old and one new strand
which of the following statements is true of chromatin
heterochromatin is highly condensed, whereas euchromatin is less compacy
in a nucleosome, the DNA is wrapped around
histones
What kind of chemical bond is found between paired bases of the DNA double helix
hydrogen
what is the role of DNA ligase in the elongation of the lagging strand during DNA replication
join Okazaki fragments together
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
_____ fixes mistakes made during DNA replication; _____ repairs damage to a preexisting double helix.
mismatch repair ... nucleotide excision repair
In nucleotide excision repair, damaged DNA is excised by _____.
nuclease
the spontaneous loss of amino groups from adenine results in hypoxanthine, an uncommon base, opposite thymine in DNA. What combination of molecules could repair such damage
nuclease, DNA ploymerase, DNA ligase
E. coli cells grown on 15N medium are transferred to 14N medium and allowed to grow for two more generations (two rounds of DNA replication). DNA extracted from these cells is centrifuged. What density distribution of DNA would you expect in this experiment?
one low-density and one intermediate-density band
which of the following synthesizes short segments of RNA
primase
Replication in prokaryotes differs from replication in eukaryotes for which of these reasons?
prokaryotic chromosomes have a single origin of replication, whereas eukaryotic chromosomes have many
In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, the key finding was that _____.
radioactively labeled phosphorus was present inside the infected bacteria
Griffith's experiments with S. pneumoniae were significant not only because they showed that traits could be transferred from one organism to another, but because they showed that _____.
the transferred traits were heritable
Cytosine makes up 38% of the nucleotides in a sample of DNA from an organism. Approximately what percentage of the nucleotides in this sample will be thymine?
12
a typical bacterial chromosome has ~4.6 million nucleotides. This supports approximately how many genes
4.4 thousand
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 (T) of the template. Which of the following represents the primer sequence?
5' A C G U U A G G 3'
An okazaki fragment has which of the following arrangements
5' RNA nucleotides, DNA nucleotides 3'
In analyzing the number of different bases in a DNA sample, which result would be consistent with the base-pairing rules
A + G = C + T
in an analysis of the nucleotide composition of DNA, which of the following will be found
A+C=G+T
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 the figure would you expect if the DNA was replicated in a conservative manner?
B
During interphase DNA is in the form of ______ and is ______.
Chromatin; less condensed than mitotic chromosomes
Chromosomes are made up of _______
DNA and proteins
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, but protein doesnt
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
A biochemist isolates and purifies various molecules needed for DNA replication. When she adds some DNA, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of DNA a few hundred nucleotides long. What has she probably left out of the mixture?
DNA ligase
Which enzyme catalyzes the elongation of a DNA strand in 5' to 3' direction?
DNA polymerase III
a new DNA strrand elongates only in the 5' to 3' direction because
DNA polymerase can only add nucleotides to the free 3' end
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
The X-ray diffraction studies conducted by _____ were key to the discovery of the structure of DNA.
Franklin
Eukaryotic telomeres replicate differently than the rest of the chromosome. This is a consequence of which of the following?
Gaps left at the 5' end of the lagging strand because of the need for a 3' onto which nucleotides can attach
The following scientists made significant contributions to our understanding of the structure and function of DNA. Place the scientists' names in the correct chronological order, starting with the first scientist(s) to make a contribution. I. Avery, McCarty, and MacLeod II. Griffith III. Hershey and Chase IV. Meselson and Stahl V. Watson and Crick
II, I, II, V, IV
In his transformation experiments, what did Griffith observe?
Mixing a heat-killed pathogenic strain of bacteria with a living non-pathogenic strain can convert some of the living cells into the pathogenic form.
Which of the following investigators was/were responsible for the following discovery? Chemicals from heat-killed S cells were purified. The chemicals were tested for the ability to transform live R cells. The transforming agent was found to be DNA
Oswald Avery, Maclyn McCarty, and Colin MacLeod
The elongation of the leading strand during DNA synthesis
depends on the action of DNA polymerase
which of the following sets of materials are required by both eukaryotes and prokaryotes for replication
double-stranded DNA, 4 kinds of dNTPs, primers, origins
To repair a thymine dimmer 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
Why do histones bind tightly to DNA
histones are positively charged, and DNA is negatively charged
What is the function of helicase in DNA replication?
it untwists the double helix and separates the two DNA strands
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 repetitive DNA sequences present at the ends of eukaryotic chromosomes are called _____.
telomeres
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
in a linear eukaryotic chromatin sample, which of the following strands is looped into domains by scaffolding
the 30 nm chromatin fiber
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
Which of the following can be determined directly from X-ray diffraction photographs of crystallized DNA
the diameter of the helix
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.
individuals with the disorder xeroderma pigmentosum are hypersensitive to sunlight. This occurs because their cells have which impaired ability
they cannot repair thymine dimers
