Download Answers to End-of-Chapter Questions – Brooker et al ARIS site

Answers to End-of-Chapter Questions – Brooker et al ARIS site
Chapter 20
Test Yourself Questions
1. Vectors used to clone genes were derived originally from
a. proteins.
b. plasmids.
c. viruses.
d. all of the above.
e. b and c only.
Answer: e. Vectors used in gene cloning were originally derived from plasmids and viruses.
2. Restriction enzymes
a. are used to cut DNA into pieces for gene cloning.
b. are naturally produced by bacteria cells to prevent viral infection.
c. produce sticky ends on DNA fragments.
d. all of the above.
e. a and c only.
Answer: d. Restriction enzymes, also called restriction endonucleases, cut DNA and produce sticky
ends on the DNA fragments. These enzymes are naturally produced in some bacteria to prevent viral
infection.
3. A DNA library produced by isolating mRNA from a cell and using reverse transcriptase to make DNA
molecules is called a __________ library.
a. genomic
b. mRNA
c. proteonomic
d. cDNA
e. chromosomal
Answer: d. cDNA libraries are produced by isolating mRNAs from a cell and producing DNA molecules
using reverse transcriptase.
4. Researchers can identify the colonies that contain the vector with the gene of interest by
a. screening the different colonies using a probe that is complementary to the gene of interest.
b. keeping records of the particular colonies that were supposedly inoculated with the
particular probe.
c. using PCR to determine the gene sequence of the DNA in the different colonies.
d. using DNA fingerprinting techniques to identify the particular gene of interest.
e. none of the above.
Answer: a. During colony hybridization, a probe that is complementary to the gene of interest is used to
identify the colonies that contain the appropriate vector.
5. A method used to detect a particular DNA sequence within a mixture of many DNA fragments is
a. PCR.
b. colony hybridization.
c. DNA fingerprinting.
d. DNA sequencing.
e. Southern blotting.
Answer: e. Southern blotting is a method that allows a researcher to detect a particular DNA sequence
in a mixture of many DNA fragments.
6. Why is Taq polymerase used in PCR rather than other DNA polymerases?
a. Taq polymerase is a synthetic enzyme that produces DNA strands at a faster rate than
natural polymerases.
b. Taq polymerase is a heat-stable form of DNA polymerase that can function after exposure
to high temperatures that are necessary for PCR.
c. Taq polymerase is easier to isolate than other DNA polymerases.
d. Taq polymerase is the DNA polymerase commonly produced by most eukaryotic cells.
e. All of the above.
Answer: b. Taq polymerase is a heat-stable form of DNA polymerase that can function after exposure to
high temperatures that are necessary for PCR.
7. The method of determining the base sequence of DNA is
a. PCR.
b. gene cloning.
c. DNA fingerprinting.
d. DNA sequencing.
e. gene mapping.
Answer: d. DNA sequencing is a method to determine the base sequence of DNA.
8. During bioremediation, microorganisms are used to
a. clone genes from eukaryotic organisms.
b. introduce correct genes into individuals with genetic diseases.
c. decrease pollutants in the environment.
d. to produce useful products such as insulin.
e. all of the above.
Answer: c. Bioremediation is the use of microorganisms to reduce pollution levels in the environment.
9. Organism that carry genes that were introduced using molecular techniques are called
a. transgenics.
b. clones.
c. mutants.
d. genetically modified organisms.
e. both a and d.
Answer: e. An organism that carries genes that were introduced using molecular techniques are called
transgenics or genetically modified organisms (GMOs).
10. DNA fingerprinting is used
a. to provide a means of precise identification of an organism, such as the identification of
specific strains of bacteria.
b. as a forensics tool to provide evidence in a criminal case.
c. to determine genetic relationships between individuals.
d. to determine the identity of an individual.
e. all of the above.
Answer: e. DNA fingerprinting is a useful tool that provides a means of identifying individuals and
determining genetic relationships between individuals.
Conceptual Questions
1. Define recombinant DNA technology and recombinant DNA.
Recombinant DNA technology: The use of laboratory techniques to isolate and manipulate fragments of
DNA.
Recombinant DNA: Any DNA molecule that has been manipulated so that it contains DNA from two or
more sources.
2. Explain how using one restriction enzyme to cut both a plasmid and a gene of interest will allow the
gene to be inserted into the plasmid.
Answer: The restriction enzyme cuts the plasmid at a specific site, leaving sticky ends. The gene of
interest, cut with the same enzyme, will have complementary sticky ends that allow hydrogen bonding
between the gene of interest and the plasmid. The connections are then made permanent using DNA
ligase that connects the DNA backbones.
3. Explain how gel electrophoresis separates DNA fragments.
Answer: An electric field is applied across the gel, causing charged molecules to migrate from one side
of the gel to the other. The smaller fragments move more quickly than the larger ones. When the run
has been completed, the fragments are separated into bands within the gel according to mass.
Experimental Questions
1. What is gene therapy? What is ADA deficiency?
Answer: Gene therapy is the introduction of cloned genes into living cells to correct genetic mutations.
The hope is that the cloned genes will correct or restore the normal gene function and thereby eliminate
the clinical effects of the disease.
ADA deficiency is a recessive genetic disorder in which an enzyme, adenosine deaminase, is not
functional. The absence of this enzyme causes a buildup of deoxyadenosine which is toxic to
lymphocytes. When lymphocytes are destroyed, a person’s immune system begins to fail leading to a
severe combined immunodeficiency disease or SCID.
2. In the investigation of Figure 20.20, how did the researchers treat ADA deficiency?
Answer: The researchers introduced normal copies of the ADA gene into lymphocytes, restoring normal
cell metabolism. The researchers isolated lymphocytes from the patient and used a viral vector to
introduce the gene into the lymphocytes. These lymphocytes were then reintroduced back into the
patient.
3. How successful was the gene therapy for ADA deficiency?
Answer: Following several rounds of treatment with gene therapy, researchers were able to document
continue production of the correct enzyme by the lymphocytes over the course of four years. However,
because the patients were also receiving other forms of treatment, it was not possible to determine if the
gene therapy reduced the negative effects of the genetic disease.
Collaborative Questions1. Discuss the use of microorganisms for bioremediation.
Answer: Bioremediation is the use of microorganisms to decrease pollutants in the environment.
Enzymes are produced by microorganisms (mostly in bacteria) to break down harmful chemicals to less
harmful ones in a process called biotransformation. As a result of this, toxic chemicals can be
transformed into nontoxic ones which is referred to as biodegradation. An example of this is the use of
microorganims to treat sewage to break it down into less harmful forms. Another example of
biodegradation is the use of microorganisms in the treatment of hazardous chemical wastes.
2. Discuss the process of molecular pharming.
Answer: In molecular pharming, agricultural animals are used to make pharmaceuticals. In most cases
domestic livestock such as sheep, cattle, and goats are use to produce proteins in their milk. This is
achieved by inserting the desired protein producing gene into the oocyte of the animal to be used. A
promoter is also inserted next to the gene so that human gene will be expressed only in the mammary
cells. This oocyte is fertilized and implanted into a surrogate mother and the offspring (the transgenic
animal) matures. Milk, which contains the desired protein, is then collected and the protein is purified
from the milk.