BIO 171 CH 13 Meiosis and Sexual Life Cycles Quiz
The overall error rate in the completed DNA molecule is approximately __________.HINT: DNA replication is amazingly accurate, but you are likely to get an error almost every time a cell divides.
1 error per 10,000,000,000 nucleotides; The rate of initial pairing errors during replication is about 1 in 100,000. This level of accuracy is then dramatically enhanced by the different proofreading mechanisms discussed in the chapter.
DNA polymerase adds nucleotides to the __________ of the leading strands, and to the __________ of the lagging strands (Okazaki fragments). HINT; The same DNA polymerase synthesizes both the leading and the lagging strands by adding nucleotides to the same free ends of growing strands.
3' end ... 3' end; Although the leading strand and lagging strand are synthesized in opposing directions with respect to the movement of the replication fork, the DNA polymerase enzyme can ONLY add nucleotides to the 3' end of a growing DNA strand.
Which of the following is correct? HINT: Specific base pairing has to do with both the size of the nitrogenous bases and their ability to form hydrogen bonds.; A- Adenine forms three covalent bonds with thymine; guanine forms two covalent bonds with cytosine. B- Adenine forms two hydrogen bonds with thymine; guanine forms three hydrogen bonds with cytosine. C- Adenine forms three hydrogen bonds with thymine; guanine forms two hydrogen bonds with cytosine. D- Adenine forms two covalent bonds with thymine; guanine forms three covalent bonds with cytosine. E- Adenine forms two hydrogen bonds with guanine; thymine forms three hydrogen bonds with cytosine.
A- NO; The bases are not connected to each other by covalent bonds. B- CORRECT; is is a consequence of the characteristics of the bases. C- NO; The characteristics of the bases will not allow this. See Figure 13.8. D- NO; The bases are not connected to each other by covalent bonds. E- NO; Think about specific base pairing. Moreover, the pairing of A with G would take up more space than allotted by the width of the DNA double helix, and the T-C pairing would take up less space.
In what way(s) is our traditional representation of DNA polymerase molecules moving like locomotives along a track inaccurate? HINT: What actually moves and what stands still during DNA replication?
BOTH: The proteins involved in replication do not move; instead, DNA is drawn through the complex. AND: DNA polymerase acts as part of a large complex of proteins, not like a single locomotive.; DNA polymerase is part of a replication machine that may be anchored to the nuclear matrix. DNA is drawn into the complex, and the newly synthesized strands are extruded.
What is the major difference between bacterial chromosomes and eukaryotic chromosomes? HINT: Is it the DNA or something else?
Bacteria have a single circular chromosome whereas eukaryotes have several linear chromosomes.; The arrangement of DNA and its association with proteins is different for prokaryotes and eukaryotes.
Which of the following enzymes could seal a nick in one strand of a double-stranded DNA molecule by creating a sugar-phosphate bond between the adjacent, unjoined nucleotides?
DNA ligase; DNA ligase is a fundamental tool in recombinant DNA technology.
What enzyme joins Okazaki fragments?
DNA ligase; Helicases unwind the DNA; polymerase synthesizes the complementary strands; ligase joins the Okazaki fragments.
The removal of the RNA primer and addition of DNA nucleotides to the 3' end of Okazaki fragments in its place is carried out by __________.HINT: There are several enzymes that can add nucleotides to DNA..
DNA polymerase I; Upon encountering the RNA primer, DNA polymerase III falls off the DNA and is replaced by DNA polymerase I.
Which of the following components is required for DNA replication?
RNA primer; In the cell, the preexisting chain, the primer needed to initiate DNA elongation, is RNA, not DNA.
Once the DNA at the replication fork is unwound by helicases, what prevents the two strands from coming back together to re-form a double helix?
Single-strand binding proteins bind the unwound DNA and prevent the double helix from re-forming.; As soon as the helicase passes, the single-strand binding proteins rapidly coat the unwound DNA and prevent the strands from coming back together.
One strand of a DNA molecule has the base sequence 5'-ATAGGT-3'. The complementary base sequence on the other strand of DNA will be 3'-_____-5'.
TATCCA; A always pairs with T, and G with C.
Which of the following enzymes is key to the automation of PCR (polymerase chain reactions)?HINT: PCR can quickly amplify any specific DNA segment within one or many DNA molecules in a test tube. What enzyme serves to "amplify" segments of existing DNA? a; restriction enzyme b; human DNA polymerase c; reverse transcriptase d; Taq polymerase e; DNA ligase
Taq polymerase; Taq polymerase is a heat-stable DNA polymerase that was isolated from the hot spring bacterium Thermus aquaticus. It is ideal for PCR because it is not denatured by the heat applied to separate DNA strands in PCR and can polymerize DNA from short, single-stranded DNA primers that are complementary to sequences at each end of the DNA sequence to be amplified.
Why were many of the early experiments on DNA carried out on viruses and bacteria?
They have relatively small genomes. They have short generation times. They can interact with each other. Their chromosomes have a simpler structure.
Who is credited with explaining the structure of the DNA double helix? HINT; The discovery was the basis of the 1962 Nobel Prize in Physiology or Medicine.
Watson and Crick;In April 1953, Watson and Crick published a one-page paper in the journal Nature elucidating their molecular model for the DNA double helix.
What technique was most helpful to Watson and Crick in developing their model for the structure of DNA?HINT: They relied on the work of Rosalind Franklin in developing their model.
X-ray crystallography; Watson and Crick based their model of DNA on insights they were able to gain from Franklin's X-ray diffraction photo.
At each end of a DNA replication bubble is __________.
a replication fork; Replication forks are found at the ends of replication bubbles.
What two enzymes are needed to produce recombinant DNA?
a restriction enzyme and a ligase; Recombinant DNA technology involves combining genes from two sources, such as different species, into a single molecule. Restriction enzymes CUTS the segments, and ligase SEALS the pieces in place.
An enzyme that cuts DNA at a symmetrical sequence of bases is called __________.
a restriction enzyme; Restriction enzymes cut DNA molecules at a limited number of specific locations, each of which contains a recognition sequence, or restriction site.
Meiosis II is similar to mitosis in that
a. DNA replicates before the division; ;sister chromatids separate during anaphase
A human cell containing 22 autosomes and a Y chromosome is
a. a sperm.
Which description of DNA replication is correct? a; Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates. b; Ligase separates the two strands of the DNA double helix. Then, DNA polymerase synthesizes the leading strand and primase synthesizes the lagging strand. c; The two strands separate, and each one receives a complementary strand of RNA. Then this RNA serves as a template for the assembly of many new strands of DNA. d; The two strands of DNA separate, and restriction enzymes cut up one strand. Then, the DNA polymerase synthesizes two new strands out of the old ones. e; Ligase assembles single-stranded codons, then polymerase knits these codons together into a DNA strand.
a; Helicases separate the two strands of the double helix, and DNA polymerases then construct two new strands using each of the original strands as templates; In the semiconservative model of DNA replication, the two strands of the parental molecule separate, and each functions as a template for the synthesis of a new complementary strand.
In DNA, the two purines are __________, and the two pyrimidines are __________.
adenine (A) and guanine (G) ... cytosine (C) and thymine (T); Purines have two rings, and pyrimidines have one.
Individuals with the disorder xeroderma pigmentosum __________.
are hypersensitive to sunlight, have difficulty repairing thymine dimers, often have inherited defects in the nucleotide excision repair system, have high rates of skin cancer; Individuals with this disorder are unusually sensitive to sunlight because they cannot repair the thymine dimers that can result from exposure to ultraviolet light.
The role of DNA polymerases in DNA replication is to __________. HINT: The suffix "-ase" refers to an enzyme. Consider the relationship of this enzyme to polymers.
attach free nucleotides to the new DNA strand; Elongation of new DNA at a replication fork is catalyzed by enzymes called DNA polymerases.
The two homologs of a pair move toward opposite poles of dividing cell during
b.
Put the following DNA-containing entities in order according to the amount of DNA found in their genomes.HINT: Are Genome size and organismal complexity related? a; bacteria, eukaryote, virus b; virus, bacteria, eukaryote c; eukaryote, virus, bacteria d; bacteria, virus, eukaryote
b; virus, bacteria, eukaryote; In general, viruses have the smallest genomes, followed by bacteria, with eukaryotes having the largest genomes.
The DNA structures of prokaryotes and eukaryotes are different in several ways, but one way in which they are the same is that __________. HINT: Why does the replication model that has been worked out for bacteria seem to hold true for prokaryotes?
both have a sugar & a phosphate group backbone; All DNA occurs as a double helix with two sugar-phosphate backbones that are antiparallel to each other.
If we continue to follow the cell lineage from question 4, then the DNA content of a single cell at metaphase of meiosis II will be a. 0.25x. b. 0.5x. c. x. d. 2x..
c.
The incorporation of an incorrect base into the DNA during replication __________.
can be repaired by the mismatch repair system; The mismatch repair system can detect and rectify incorrectly incorporated bases.
If the DNA content of a diploid cell in the G1 phase of the cell cycle is x, then the DNA content of the same cell at metaphase of meiosis I will be: a. 0.25x. b. 0.5x. c. x. d. 2x.
d.
During the replication of DNA, __________. a: the reaction is catalyzed by RNA polymerase b: errors never occur c: only one strand of the molecule acts as a template d: both strands of a molecule act as templates e: the cell undergoes mitosis
d: both strands of a molecule act as templates; When a cell copies a DNA molecule, each strand serves as a template for ordering nucleotides into a new complementary strand.
Bacteria use restriction enzymes to:
destroy foreign DNA; Restriction enzymes are used to protect bacteria against intruding DNA from other organisms.
In the polymerase chain reaction (PCR), the sequence of bases in the primers is important because it __________. HINT: Consider the role of primers in DNA replication.
determines which segment of the genome will be amplified; PCR starts with double-stranded DNA that is to be copied. Primers, necessary for DNA polymerase to initiate DNA synthesis, are added to the mixture. They are complementary to the ends of the targeted DNA and determine the segment of DNA to be amplified.
Which of the following statements about replication origins is correct? a; In bacteria, the DNA sequence at the origin is recognized by specific proteins that then bind to the origin. b; The two strands of DNA at the origin are separated, allowing the formation of a replication bubble. c; Bacterial chromosomes have a single origin, but eukaryotic chromosomes have many origins. d; In both prokaryotes and eukaryotes, replication proceeds in both directions from each origin. e; All of the listed responses are correct.
e; All of the listed responses are correct; What events have to occur to start replication?
Gene cloning is crucial to any application involving one gene because __________.
genes occupy only a small proportion of the chromosomal DNA in eukaryotes, the rest being noncoding nucleotide sequences naturally occurring DNA molecules are very long and contain many genes it provides a means to produce many copies of a gene in short period of time it provides a means to produce large quantities of its protein product : Because a typical gene is usually a very small part of the total DNA of a cell, scientists use gene cloning procedures to amplify specific genes for further genetic analysis, for recombinant applications, and as a means to generate large quantities of their protein products for human use.
During Griffith's experiments with Streptococcus pneumoniae in mice, material from __________ bacteria transformed __________ bacteria.
heat-killed virulent ... living nonvirulent ; Griffith found that some of the living nonvirulent cells were converted to the virulent form.
After the formation of a replication bubble, which of the following is the correct sequence of enzymes used for the synthesis of the lagging DNA strand?
helicases, primase, DNA polymerases, ligase; First the double helix is unwound; primase makes the RNA primer; DNA polymerases elongate the growing strand and replace the RNA primer with DNA; and DNA ligase joins the Okazaki fragments.
Which of the following attributes of DNA is most crucial to its accurate duplication? HINT: The ability to make accurate copies had to be inherent in DNA's structure.
its specific complementary base pairing and hydrogen bonding; The hydrogen bonding makes it easy to separate the two strands. Specific complementary base pairing ensures that an accurate strand will be constructed on each template strand.
The rate of elongation in prokaryotes is __________ the rate in eukaryotes. HINT: The eukaryotic replication machinery is more complex than the prokaryotic machinery.
much faster than; The rate of elongation is about 500 nucleotides per second in bacteria and about 50 nucleotides per second in human cells.
Which set of enzymes is involved in nucleotide excision repair?
nuclease, DNA polymerase, and ligase
The "beads on a string" seen in interphase chromatin are __________.HINT: What stage of DNA packing do they represent?
nucleosomes; Nucleosomes are complexes of DNA wrapped around eight histone molecules.
A molecular biologist has isolated a short segment of DNA that she wants to replicate in vitro. First she heats the DNA, which separates the two strands, and then she adds __________. HINT: What is required for a single round of PCR?
nucleotides, primers, and polymerase; PCR requires a pool of nucleotide building blocks, primers to initiate DNA synthesis, and polymerase to continue elongation of the new strands.
Monomers for the synthesis of DNA are called __________.
nucleotides; Each nucleotide unit of DNA consists of a nitrogenous base (A, G, C, or T), the sugar deoxyribose, and a phosphate group.
The two strands of a DNA double helix are antiparallel. This means that __________. HINT: Relate the term antiparallel to traffic flow on highways.
one strand runs in the 5' to 3' direction, and the other runs in the 3' to 5' direction; This allows the two strands to fit together properly.
The experiments of Meselson and Stahl showed that DNA __________.
replicates in a semiconservative fashion; In the semiconservative model of DNA replication, the two strands of the parental molecule separate. Each functions as a template for the synthesis of a new complementary strand.
In genetic engineering, "sticky end" refers to __________.HINT: Property of water
short bits of single-stranded DNA left at the end of DNA molecules cut by restriction enzymes; The sticky ends of restriction fragments allow hydrogen bonding with complementary single-stranded stretches on other DNA molecules cut with the same enzyme.
When a typical restriction enzyme cuts a DNA molecule, the cuts are staggered so that the DNA fragments have single-stranded ends. This is important in recombinant DNA work because __________.
the fragments will bond to other fragments with complementary single-stranded ends; The sticky ends of restriction fragments allow hydrogen bonding with complementary single-stranded stretches on other DNA molecules cut with the same enzyme.
In an important experiment, a radioactively labeled bacteriophage was allowed to infect bacteria. In a first trial, the phage contained radioactive DNA, and radioactivity was detected inside the bacteria. Next, phage containing radioactive protein was used, and the radioactivity was not detected inside the bacteria. These experiments led to the conclusion that __________.
the genetic material of the phage is DNA; In order to replicate, viral material must enter a bacterial cell. This experiment showed that the viral DNA had entered the bacterial cell.
A scientist assembles a bacteriophage with the protein coat of phage T2 and the DNA of phage T4. If this composite phage were allowed to infect a bacterium, the phages produced in the host cell would have __________. HINT: Consider the famous Hershey and Chase experiment.
the protein and DNA of T4
Chargaff found that for DNA _____.HINT: Purines always pair with pyrimidines.
the ratio of A to T is close to 1:1 and the ratio of G to C is close to 1:1
The information in DNA is contained in __________.HINT: Consider what aspect of DNA can exhibit variation.
the sequence of nucleotides along the length of the two strands of the DNA molecule; Although base-pairing rules dictate the combinations of nitrogenous bases forming the rungs of the double helix, they do not restrict the sequence of nucleotides along each strand, and the linear sequence of bases can be varied in countless ways.
In the polymerase chain reaction (PCR) technique, a heating phase and a cooling phase alternate. An original sample of DNA would have to pass through how many total rounds of heating and cooling before a sample is increased eight times in quantity?
three; 2³=8; The amount of DNA doubles with each round. After one round, there is twice as much as was originally present. After two rounds, four times as much. After three rounds, eight times as much would be present.
The unwinding of DNA at the replication fork causes twisting and strain in the DNA ahead of the fork, which is relieved by an enzyme called __________. HINT: When this enzyme has done its job, the DNA should be "equal" to what it was prior to unwinding.
topoisomerase; Topoisomerase cuts the DNA and allows it to spin around its central axis, which relieves the strain caused by twisting.
Avery and his colleagues' 1944 experiment showed that DNA __________.
was the substance that transformed the bacteria in Griffith's experiment;
