Chapter 20 Questions Flashcards
1
Q
Gene cloning is crucial to any application involving one gene because _____.
A
- naturally occurring DNA molecules are very long and contain many genes
- it provides a means to produce large quantities of its protein product
- genes occupy only a small proportion of the chromosomal DNA in eukaryotes, the rest being noncoding nucleotide sequences
- it provides a means to produce many copies of a gene in short period of time
2
Q
What is an advantage to using a bacterial artificial chromosome (BAC) for generating a genomic library compared to a plasmid or phage that has historically been used for this process?
A
- BACs carry DNA fragments much larger than plasmids or phages and greatly minimize the number of clones needed to make up the genomic library.
- The use of BACs reduces the frequency with which specific genes will be cut within the coding region by restriction enzymes and divided up among two or more clones.
3
Q
In which of the following would it be advantageous to create and work with a cDNA (complementary DNA) library rather than a genomic library?
A
a study of a protein involved in eye development of a salamander and the regulation of the gene that expresses it
4
Q
The expression of the PAX-6 gene when vertebrate and fruit fly versions of the gene are exchanged between these animal groups illustrates _____.
A
the common ancestry in the evolution of these animal groups
5
Q
Which of the following enzymes is key to the automation of PCR (polymerase chain reactions)?
A
Taq polymerase
6
Q
Bacteria use restriction enzymes to _____.
A
destroy foreign DNA
7
Q
An enzyme that cuts DNA at a symmetrical sequence of bases is called _____.
A
a restriction enzyme
8
Q
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 _____.
A
the fragments will bond to other fragments with complementary single-stranded ends
9
Q
In genetic engineering, “sticky end” refers to _____.
A
short bits of single-stranded DNA left at the end of DNA molecules cut by restriction enzymes
10
Q
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?
A
DNA ligase
-DNA ligase is a fundamental tool in recombinant DNA technology.
11
Q
To create recombinant DNA with long-term stability, it is necessary to have which of the following in the test tube?
A
DNA ligase
12
Q
What two enzymes are needed to produce recombinant DNA?
A
a restriction enzyme and a ligase
13
Q
In recombinant methods, the term “vector” refers to _____.
A
a plasmid or other agent used to transfer DNA into a living cell
14
Q
Which arrangement of the following four enzymes represents the order in which they would be used in a typical gene-cloning experiment resulting in the insertion of a cDNA into a bacterial plasmid? Begin with the gene’s mRNA transcript.
A
reverse transcriptase, DNA polymerase, restriction enzyme, DNA ligase
15
Q
A scientist wishing to create an organism capable of breaking down several kinds of toxic waste combines genes from several species of bacteria to create a single “superbacterium.” Which of the following would be needed to do this?
A
- nucleic acid probes
- DNA ligase
- plasmids
- restriction enzymes
16
Q
A nucleic acid probe is used to _____.
A
identify genes that have been inserted into bacterial plasmids or separated by electrophoresis
17
Q
What is the source of the reverse transcriptase used in recombinant DNA technology?
A
retroviruses
18
Q
Because eukaryotic genes contain introns, they cannot be translated by bacteria, which lack RNA-splicing machinery. But if you want to engineer a bacterium to produce a eukaryotic protein, you can synthesize a gene without introns. A good way to do this is to _____.
A
work backward from mRNA to make a version of the gene without introns
19
Q
DNA synthesized using an RNA template is called _____.
A
cDNA
20
Q
In the polymerase chain reaction (PCR), the sequence of bases in the primers is important because it _____.
A
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.
21
Q
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 _____.
A
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.
22
Q
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?
A
three
23
Q
Single nucleotide polymorphisms (SNPs) _____.
A
- are single base-pair variations in the genomes of the human population
- are genetic markers used to study the genetic basis for disease
- are small nucleotide differences among individuals located in coding and non-coding sequences in the genome
- can be the molecular basis for different alleles
24
Q
Separating DNA fragments by gel electrophoresis is useful for which of the following?
A
- identifying DNA fragments for RFLP analysis
- purifying specific DNA fragments
- distinguishing between different alleles of a gene
- identifying a plasmid or a virus by examining its restriction fragment pattern
25
Southern blotting is _____.
a technique used to study RFLPs
26
Which of the following is the first step of the Southern blotting procedure?
digesting the DNA with a restriction enzyme
27
The dideoxyribonucleotide chain-termination method _____.
produces a ladder of DNA fragments, with each individual band labeled with one of four different fluorescent tags
-Each band differs in size by a single nucleotide, and the particular fluorescent tag of the band indicates the identity of the final nucleotide.
28
The term "RFLP" stands for _____.
restriction fragment length polymorphism
-RFLPs, or restriction fragment length polymorphisms, are small differences in homologous DNA sequences that result in different restriction fragment patterns.
29
RFLPs have been tremendously useful for genomic mapping studies because _____.
they are not restricted to genes, and are abundantly scattered throughout the genome
30
The efficiency of cloning, and the ability to generate healthy cloned animals, has been largely hampered by the difficulty of _____.
completely reversing epigenetic alterations in donor cell nuclei such as DNA methylation and chromatin packing
-It is thought that the subtle abnormalities that often affect cloned animals result from an inability to completely reverse these alterations.
31
"Therapeutic cloning" refers to _____.
the use of cloned embryos as a source of stem cells that could be used to treat disease
-Such cells could potentially be used to treat diseases such as Parkinson's disease, Huntington's disease, and diabetes. Nevertheless, the prospect of therapeutic cloning remains quite controversial.
32
Nuclear transplantation involves _____.
removing the nucleus of an egg cell and replacing it with the nucleus of a somatic cell
33
_____ can give rise to any type of cell whereas _____ can give rise to a subset of cell types.
Embryonic stem cells ... adult stem cells
34
During the process of differentiation, cells _____.
express different genes in response to cell signaling
35
Dolly, the sheep, was cloned from an adult cell. She had a number of health problems and died at a relatively young age. Three mules that were born in 2003 were cloned from fetal cells. If it turns out that the mules remain healthy and live normal lives, how would this outcome tie in with Gurdon's observations with tadpoles?
Gurdon found that the ability of a transplanted nucleus to direct normal development was inversely related to the age of the donor.
-Gurdon found that nuclei from older donor cells were unlikely to correctly direct differentiation.
36
All of the following are true regarding induced pluripotent stem (iPS) cells except _____.
iPS cells have been demonstrated to function identically to embryonic stems cells
37
All of the following are current applications of DNA technology in medicine except _____.
clinical use of iPS cells harvested from organ-impaired individuals for the culturing and transplantation of a functioning organ in the diseased individual
-Although iPS cell technology holds promise for this type of application, there is much we don't know about how to direct iPS cells into specific cell types to form tissues and organs.
38
All of the following are current applications of DNA technology in medicine
- use of genome-wide association studies to identify SNPs (single-nucleotide polymorphisms) linked to disease
- use of microarray assays to analyze the expression patterns of genes associated a type of cancer
- use of retroviruses to introduce normal alleles of genes into diseased cells for disorders involving one defective gene
- genetically engineering organisms, from bacteria to goats, into protein factories that produce vital human proteins such as insulin, anticlotting agents, and human growth hormone
39
A genetic marker is _____.
a particular nucleotide sequence at a particular locus whose inheritance can be followed
40
Human nerve cells differ from human muscle cells because different sets of genes are expressed; in each type of cell, different genes are transcribed into mRNA and translated into protein. Which of the following techniques would be the most efficient way to identify the genes that these cells express?
DNA microarray assays
41
Gene therapy involves _____.
adding a functioning version of a defective gene to the cells of an individual
-In gene therapy, a new, functional gene is inserted into the somatic cells of the tissue affected by the disorder.
42
A molecular biologist used a retroviral vector to introduce a gene coding for a certain human enzyme into mouse cells. One cell line was isolated that was able to make the human enzyme, but it had lost the ability to express an endogenous, normally expressed gene in the process. What is the best explanation for these results?
The virus inserted the gene encoding the human enzyme within the sequence of a normally expressed endogenous gene.
43
DNA fingerprints are used to determine whether Sam could be the father of Becky's baby. Sam is not the father if _____ genetic fingerprint shows some bands not present in _____ genetic fingerprint.
the baby's ... Sam's or Becky's
-Because a baby receives only half of its genes from each parent, you would expect the DNA of each parent to show some bands not seen in their child.
44
DNA fingerprints used as evidence in a murder trial look something like supermarket bar codes. The pattern of bars in a DNA fingerprint shows _____.
the presence of various-sized fragments of DNA
-DNA fingerprinting does not involve nucleotide sequencing.
45
Which of the following would be considered a transgenic organism?
a rat with rabbit hemoglobin genes
-Transgenic refers to the origin of the genes in the genome, not their expression.
46
Transgenic organisms can be scientifically or commercially useful only if _____.
the inserted ("foreign") gene is expressed in the host organism
47
In genetic engineering, the highly active plasmid from Agrobacterium tumefaciens is used to _____.
insert genes of interest into plant chromosomes
-The usual DNA vector for moving genes into plants is a plasmid of the bacterium Agrobacterium tumefaciens.
48
Which of the following tools of recombinant DNA technology is correctly paired with its use?
- restriction enzyme--analysis of RFLPs
- DNA polymerase--polymerase chain reaction to amplify sections of DNA
- reverse transcriptase--production of cDNA from mRNA
- electrophoresis--separation of DNA fragments
49
Which of the following tools of recombinant DNA technology is INCORRECTLY paired with its use?
DNA ligase-cutting DNA, creating sticky ends of restriction fragments
50
Plants are more readily manipulated by genetic engineering than are animals because
a somatic plant cell can often give rise to a complete plant
51
A paleontologist has recovered a bit of tissue from the 400-year-old preserved skin of an extinct dodo (a bird). To compare a specific region of the DNA from the sample with DNA from living birds, which of the following would be most useful for increasing the amount of dodo DNA available for testing?
polymerase chain reaction (PCR)
52
DNA technology has many medical applications. Which of the following are done routinely at present?
- production of hormones for treating diabetes and dwarfism
- production of microbes that can metabolize toxins
- prenatal identification of genetic disease alleles
- genetic testing for carriers of harmful alleles
53
DNA technology has many medical applications. Which of the following is NOT done routinely at present?
introduction of genetically engineered genes into human gametes
54
In recombinant DNA methods, the term vector can refer to
a plasmid used to transfer DNA into a living cell
55
Which of the following would be true of cDNA produced using human brain tissue as the starting material?
- it could be amplified by the polymerase chain reaction
- it was produced from mRNA using reverse transcriptase
- It could be used as a probe to detect genes expressed in the brain
- it lacks the introns of the human genes
56
Which of the following would NOT be true of cDNA produced using human brain tissue as the starting material?
it could be used to create a complete genomic library
57
Expression of a cloned eukaryotic gene in a bacterial cell involves many challenges. The use of mRNA and reverse transcriptase is part of a strategy to solve the problem of
post-transcriptional processing
58
Which of the following sequences in double-stranded DNA is most likely to be recognized as a cutting site for a restriction enzyme?
GGCC
| CCGG
59
Which of the following is an example of "recombinant DNA technology?"
introducing a human gene into a bacterial plasmid
-Recombinant DNA technology involves combining DNA from different sources into a single molecule, such as inserting a gene from one species into a plasmid from another.
60
In recombinant DNA experiments, what is used to cut pieces of DNA and what joins the resulting fragments to form recombinant DNA?
a restriction enzyme ... DNA ligase
-Restriction enzymes cut DNA molecules at specific points; in most cases, the restriction fragments have sticky ends that can base-pair with complementary sticky ends. The joined segments are then covalently fused by DNA ligase.
61
cDNA is synthesized from what molecule using an enzyme known as what?
mRNA ... reverse transcriptase
-Reverse transcriptase is a viral enzyme that can synthesize DNA from an RNA template.
62
Archaeologists unearthed a human skull with a small dried fragment of the scalp still attached. They extracted a tiny amount of DNA from the scalp tissue. How could they obtain sufficient DNA for an analysis of the ancient human's genes?
Use the polymerase chain reaction.
-PCR is a method of DNA amplification.
63
Gel electrophoresis separates DNA fragments on the basis of what characteristic?
length
-As the DNA fragments move through the gel, longer fragments are impeded more than shorter fragments, producing characteristic banded patterns in the gel.
64
Which of the following is true of stem cells?
- Their use is highly controversial.
- They can differentiate to produce many different kinds of specialized cells.
- They can reproduce indefinitely in culture.
- They can be found in both embryonic and adult tissues.
65
If cells from a carrot are removed and placed in a culture medium, they can develop into a normal adult plant. This demonstrates that carrot cells _____.
retain all the genes that were in the zygote that developed into the original plant
-Furthermore, the carrot cells are totipotent.
66
You are a member of the jury for a murder case. The prosecution has presented DNA evidence linking the defendant to the crime scene. The defense claims that DNA evidence using STR analysis with 13 markers is not sufficient to reliably distinguish between people. What do you think?
The prosecution is right. STR analysis with 13 markers gives a 1 in 10 billion or greater chance that two people will have the same pattern. This person was at the crime scene.
-Given the current population of the Earth, STR analysis with 13 markers should be sufficient to distinguish between any two people (excluding identical twins, of course) on the planet.
67
What is the most commonly used vector for introducing transgenes into plants?
the Ti plasmid
-The Ti plasmid comes from Agrobacterium tumefaciens, and it is effective at integrating with the host cell's DNA.
68
In order to insert a human gene into a plasmid, both must _____
be cut by the same restriction enzyme
-Doing so will result in the formation of complementary sticky ends.
69
What enzyme forms covalent bonds between restriction fragments?
DNA ligase
-DNA ligase catalyzes the formation of covalent bonds between restriction fragments.
70
Transformation is the process by which
a bacterium takes up a plasmid from the surrounding solution.
71
Cloning occurs with the replication of a
recombinant plasmid.
72
What defect causes pituitary dwarfism?
Lack of growth hormone
-Affected individuals produce little or no growth hormone.
73
What is genetic cloning?
A method to produce many copies of a gene
-Genetic cloning is the process by which many identical copies of a gene are produced.
74
True or false? The use of growth hormone isolated from cadavers was banned mainly because there were not enough cadavers to supply the hormone.
False
-The use of growth hormone isolated from cadavers was banned mainly because the isolated hormone was potentially contaminated with prion proteins.
75
Which of the following statements best describes the function of reverse transcriptase?
It makes complementary DNA (cDNA) from mRNA.
-The function of reverse transcriptase is similar to the reverse of transcription; it makes a single strand of complementary DNA (cDNA) from mRNA.
76
Which of the following steps would be performed last when screening a cDNA library?
Match the region of radioactivity on the filter with the corresponding plate.
-This step allows researchers to match the colony on the filter with the colony of the bacterial plate so the correct colony can be grown for further study. It would be the last step in screening a cDNA library.
77
How can large quantities of protein be produced from a bacterial colony containing the gene of interest?
Put a cDNA encoding the protein into a plasmid with a bacterial promoter sequence.
-Once a cDNA is put into a plasmid with a bacterial promoter, the bacteria will transcribe and translate the gene.
78
True or false? The term "sticky ends" refers to the overhanging ends on DNA that are generated by restriction enzymes, which can base pair with any DNA molecules that contain complementary sticky ends.
True
-Restriction enzymes cut DNA and generate "sticky ends," which can then base pair with DNA molecules that contain the same sticky ends.
79
The unpaired nucleotides produced by the action of restriction enzymes are referred to as _____.
sticky ends
-They are called sticky ends since they will "stick" to a complementary single-stranded sequence.
80
The matching of sticky ends follows the rules of
specific base pairing.
81
What is the polymerase chain reaction (PCR)?
A method to amplify a fragment of DNA.
-PCR is an in vitro DNA synthesis reaction that produces many copies of a single DNA fragment.
82
True or false? Comparison of the sequences of the same gene across species can give some insight into the existence of a common ancestor with that gene.
True
-DNA sequence comparisons are a powerful tool by which to estimate how closely related different species are along the evolutionary timeline.
83
True or false? The Taq enzyme is a type of DNA polymerase that allows researchers to separate the DNA strands during the annealing step of the PCR cycle without destroying the polymerase.
False
-Taq polymerase is derived from a species of bacteria living in hot springs, which makes it stable at the high temperature required for the denaturation step of PCR.
84
During which step in the PCR cycle are nucleotides used?
Extension.
-Nucleotides are used to synthesize the complementary strand to the DNA template during the extension step.
85
During which step in the PCR cycle do primers form bonds with a single-stranded template?
Annealing.
-Primers form hydrogen bonds with the single-stranded DNA template during the annealing step.
86
In Gel Electrophoresis of DNA
The shorter the DNA molecule, the farther it moves.
87
In gel electrophoresis DNA molecules migrate from _____ to _____ ends of the gel.
negative ... positive
-An electrical current is generated across the gel, and DNA molecules migrate from the negative end toward the positive end.
88
Why is golden rice pale yellow in color?
It is rich in beta-carotene.
-Beta-carotene confers a yellow color on the rice.
89
Which of these is a symptom of vitamin A deficiency?
blindness
-Chronic vitamin A deficiency can lead to blindness.
90
Which of these is a vitamin A precursor?
beta-carotene
-The body can convert beta-carotene into vitamin A.
91
The transfer of antibiotic-resistant genes from genetically engineered bacteria to disease-causing bacteria _____.
seems unlikely.
-It seems unlikely to occur and there is no evidence that it has occurred.
92
PCR is a method for
amplifying DNA.
93
DNA normally moves down through a gel due to
the attraction of opposite charges.
