Which of these is a difference between a DNA and an RNA molecule?
DNA is usually double-stranded, whereas RNA is usually single-stranded
Which of these nitrogenous bases is found in DNA but not in RNA?
thymine
In a nucleotide, the nitrogenous base is attached to the sugar's _____ carbon and the phosphate group is attached to the sugar's _____ carbon.
1' ... 5'
Nucleic acids are assembled in the _____ direction.
5' to 3'
In a DNA double helix an adenine of one strand always pairs with a(n) _____ of the complementary strand, and a guanine of one strand always pairs with a(n) _____ of the complementary strand.
thymine ... cytosine
Who demonstrated that DNA is the genetic material of the T2 phage?
Hershey and Chase
The radioactive isotope 32P labels the T2 phage's _____.
DNA
Hershey and Chase used _____ to radioactively label the T2 phage's proteins.
35S
After allowing phages grown with bacteria in a medium that contained 32P and 35S, Hershey and Chase used a centrifuge to separate the phage ghosts from the infected cell. They then examined the infected cells and found that they contained _____, which dem
labeled DNA ... DNA
Griffith's experiments with S. pneumoniae were significant because they showed that traits could be transferred from one organism to another. What else did he find that was significant?
The transferred traits were heritable
In the Hershey and Chase experiment that helped confirm that DNA, not protein, was the hereditary material, what was the key finding?
Radioactively labeled phosphorus was present inside the infected bacteria.
Who conducted the X-ray diffraction studies that were key to the discovery of the structure of DNA?
Franklin
In the 1950s, when Watson and Crick were working on their model of DNA, which concepts were well accepted by the scientific community?
Chromosomes are found in the nucleus, Chromosomes are made up of protein and nucleic acid, Genes are located on chromosomes.
What are the chemical components of a DNA molecule?
phosphate group, sugar, nitrogenous base
In the early 1950s, many researchers were racing to describe the structure of DNA using different approaches. Which of the following statements is true?
Jim Watson and Francis Crick built theoretical models, incorporating current knowledge about chemical bonding and X-ray data.
Early, flawed DNA models proposed by Watson and Crick and by Linus Pauling correctly described which property of DNA?
DNA is composed of sugars, phosphates, and bases.
What did Rosalind Franklin's famous photo 51 show?
DNA is a helix.
Erwin Chargaff observed that the proportions of adenine (A) and thymine (T) bases were always equal, as were the proportion of guanine (G) and cytosine (C). Chargaff's observation suggests which of the following statements?
The data suggest that A would always pair with T and G would always pair with C in a DNA molecule
What did the structure of DNA's double helix suggest about DNA's properties?
DNA can change. Errors in copying can result in changes in the DNA sequence that could be inherited by future generations, DNA can be replicated by making complementary copies of each strand, DNA stores genetic information in the sequence of its bases.
After DNA replication is completed, _____.
each new DNA double helix consists of one old DNA strand and one new DNA strand
The first step in the replication of DNA is catalyzed by _____.
helicase
The action of helicase creates _____.
replication forks and replication bubbles
Why is the new DNA strand complementary to the 3' to 5' strands assembled in short segments?
DNA polymerase can assemble DNA only in the 5' to 3' direction
The synthesis of a new strand begins with the synthesis of a(n) _____
RNA primer complementary to a preexisting DNA strand
An old DNA strand is used as a _____ for the assembly of a new DNA strand.
template
Short segments of newly synthesized DNA are joined into a continuous strand by _____.
ligase
After DNA replication is completed, _____.
each new DNA double helix consists of one old DNA strand and one new DNA strand
What catalyzes DNA synthesis?
DNA polymerase
Which of the following statements about DNA synthesis is true?
Primers are short sequences that allow the initiation of DNA synthesis.
Which part of a deoxynucleoside triphosphate (dNTP) molecule provides the energy for DNA synthesis?
phosphate groups
Which of the following enzymes creates a primer for DNA polymerase?
primase
Which of the following statements about Okazaki fragments in E. coli is true?
They are formed on the lagging strand of DNA.
Which of the following enzymes is important for relieving the tension in a helix as it unwinds during DNA synthesis?
topoisomerase
True or false? Single-stranded DNA molecules are said to be antiparallel when they are lined up next to each other but oriented in opposite directions.
true
DNA replication is said to be semiconservative. What does this mean?
Each new double helix consists of one old and one new strand.
What is the function of helicase in DNA replication?
It untwists the double helix and separates the two DNA strands.
What process repairs damage to a preexisting double helix?
nucleotide excision repair
In nucleotide excision repair, damaged DNA is excised by what enzyme(s)?
nuclease
What are the repetitive DNA sequences present at the ends of eukaryotic chromosomes called?
telomeres
What are chromosomes made of?
DNA and proteins
Which of the following is true of DNA during interphase?
It exists as chromatin and is less condensed than mitotic chromosomes.
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.
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.
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
The elongation of the leading strand during DNA synthesis
depends on the action of DNA polymerase
In a nucleosome, the DNA is wrapped around
histones
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 experime
one low-density and one intermediate-density band
A biochemist isolates, purifies, and combines in a test tube a variety of molecules needed for DNA replication. When she adds some DNA to the mixture, replication occurs, but each DNA molecule consists of a normal strand paired with numerous segments of D
DNA ligase
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
DNA is a self-replicating molecule. What accounts for this important property of DNA?
The nitrogenous bases of the double helix are paired in specific combinations: A with T and G with C.
During DNA replication, the leading strand is synthesized continuously, whereas the lagging strand is synthesized as Okazaki fragments. Why is this so?
DNA synthesis can take place only in the 5' to 3' direction.
Nucleotides are added to a growing DNA strand as nucleoside triphosphates. What is the significance of this fact?
Hydrolysis of the two phosphate groups (P-Pi) and DNA polymerization are a coupled exergonic reaction.
Meselson and Stahl cultured E. coli for several generations in a medium with a heavy isotope of nitrogen, 15N. They transferred the bacteria to a medium with a light isotope of nitrogen, 14 N. After two rounds of DNA replication, half the DNA molecules we
DNA replication is semiconservative.
Select the most accurate statement describing DNA replication complexes.
DNA replication complexes are grouped into factories, which are anchored to the nuclear matrix