Question 1

Which of the following is not a purpose of gene therapy?&#10;A) Delete an abnormal gene&#10;B) Turning on or off a gene&#10;C) Repair an abnormal gene&#10;D) Exchange an abnormal gene with a normal gene

Accepted Answer

Gene therapy is not being used to delete an abnormal gene. Answer B is incorrect, regulation of a gene is a purpose of gene therapy. Answer C is incorrect, repairing an abnormal gene by reversing the mutation is a purpose of gene therapy. Answer D is incorrect, exchanging an abnormal gene with a normal gene is a purpose of gene therapy. Answer A is correct.

Question 2

The process of donated DNA entering the target cell to begin expression through a virus is known as?&#10;A) Transduction&#10;B) Conjugation&#10;C) Transformation&#10;D) Recombination

Accepted Answer

Transduction is the process in which DNA is transferred to another cell which enables the target cell to begin expression. Answer B is incorrect, conjugation is the transfer of all or some of the donor's DNA into the target cell through mating. Answer C is incorrect, transformation is the process in which the target cell uptakes extracellular DNA and incorporates it. Answer D is incorrect, recombination is the mixing of the donor and recipient's genome to form a new genome. Answer A is correct.

Question 3

Which of the following denotes a mutation that results in a nonfunctional or missing gene?&#10;A) Gain of function&#10;B) Loss of function&#10;C) Missense mutation&#10;D) Nonsense mutation

Accepted Answer

Loss of function mutations result in a decrease of or complete absence of a gene. Answer A is incorrect because gain of function mutations result in a new gene function or increased gene activity. Answer C is incorrect because missense mutations are due to the exchange of a nucleotide in a gene; this results in a code for a different amino acid which eventually alters the protein product, possibly rendering the protein nonfunctional. Answer D is incorrect because nonsense mutations occur when a nucleotide is exchanged and the codon sequence is changed to a "stop" codon, prematurely stopping the construction of a protein. Answer B is correct.

Question 4

A vector is a means to deliver a normal gene to a target cell. Which is an example of a commonly used vector for gene therapy?&#10;A) Pseudomonas&#10;B) Candida&#10;C) Herpes simplex&#10;D) Giardia

Accepted Answer

Vectors deliver a therapeutic gene to cells where it can then be integrated and alter the cell's gene expression; most vectors are viruses. Answer A is incorrect because Pseudomonas is a type of bacteria. Answer B is incorrect because Candida is a type of yeast. Answer D is incorrect because Giardia is a type of parasite. Answer C is correct.

Question 5

What is a potential drawback of using retroviruses to deliver gene therapy?&#10;A) Tumor formation&#10;B) Suppressed immune system&#10;C) Recurrent fever&#10;D) Erythemia multiforme

Accepted Answer

Retroviruses can activate proto-oncogenes while integrating in host's DNA, leading to tumor formation. Answer B is incorrect because although gene therapy can lead to a viral infection, it is not known to cause a suppressed immune system. Answer C is incorrect because gene therapy has not been linked to recurrent fevers. Answer D is incorrect because erythema multiforme is not an associated risk of gene therapy. Answer A is correct.

Question 6

A 5-year-old white male presents to the ER with shortness of breath. He has a history of recurrent respiratory infections and pancreatitis. A CXR reveals hyperinflation and peribronchial thickening. He has an abnormal sweat chloride test. What gene is most likely affected?

A) CFTR
B) AAT
C) FGFR3
D) JAK3

Accepted Answer

The patient has cystic fibrosis. Cystic fibrosis is caused by a mutation in the CFTR gene (cystic fibrosis transmembrane conductance regulator). Answer B is incorrect because a mutation in AAT (alpha- 1 antitrypsin) is not actually a gene but a protein associated with emphysema. Answer C is incorrect because a mutation of FGFR3 (fibroblast growth factor receptor 3) results in achondroplasia which is a common cause of dwarfism. Answer D is incorrect because a mutation in JAK3 is responsible for severe combined immunodeficiency (SCID). Answer A is correct.

Question 7

A 58-year-old white male is concerned about his recent 20-pound weight loss and recurrent fevers at night. On exam, he has splenomegaly. His CBC shows a WBC count of 95,000 with 20% blasts. Upon chromosomal analysis, it was determined that the there is a translocation of chromosomes 9 and 22. He was diagnosed with chronic myelogenous leukemia. What gene is associated with this disease?

A) BRCA 2
B) BCR/ABL
C) BRCA 1
D) P53

Accepted Answer

The patient described has chronic myelogenous leukemia and the gene associated with this disease is bcr/abl. Answer A is incorrect, BRCA2 is linked to breast cancer, ovarian cancer, prostate cancer, pancreatic cancer, and melanoma. Answer C is incorrect, BRCA1 is linked to breast cancer, ovarian cancer, prostate cancer, pancreatic cancer, and colon cancer. Answer D is incorrect because p53 is a tumor suppressor gene related to Li-Fraumeni syndrome. Answer B is correct.

Question 8

Which of the following can prevent an abnormal mRNA strand from translating a harmful protein, such as oncogenes?&#10;A) Vector&#10;B) Liposome&#10;C) Ribozyme&#10;D) Oligonucleotide

Accepted Answer

Oligonucleotides are being used to prevent oncogenes in colorectal and pancreatic cancer, from being expressed. Answer A is incorrect because vectors are the means in which DNA is delivered to target cells. Answer B is incorrect because liposomes are non-viral vectors that can deliver DNA by endocytosis. Answer C is incorrect because ribozymes can down regulate the production of an abnormal gene. Answer D is correct.

Question 9

Which of the following is an example of a vector that can enter non-dividing cells through pores in its membrane?&#10;A) Herpes simplex virus&#10;B) Parvovirus&#10;C) Adenovirus&#10;D) Human immunodeficiency virus

Accepted Answer

The type of vector described is a lentivirus. An example of a lentivirus is HIV. Answer A is incorrect because herpes simplex viruses are neurotropic viruses that can infect neurons, but not through pores. Answer B is incorrect because Parvovirus is considered a parvoviridae virus and works by integrating genes at specific sites on chromosomes. Answer C is incorrect because adenoviruses can infect various cells but are not become integrated into the target's cells genome, but do not use pores. Answer D is correct.

Question 10

What allows the production of viral copies when retroviruses are used as a vector targeting dividing somatic cells?&#10;A) Transduction&#10;B) Packaging cells&#10;C) Viral invasion&#10;D) Modification

Accepted Answer

When retroviruses are modified, they lose the ability to replicate by themselves. Packaging cells provide the necessary genes retroviruses need for replication. Answer A is incorrect because transduction is the process in which DNA is transferred to another cell which enables the target cell to begin expression. Answer C is incorrect because modified retroviruses are incapable of replicating by themselves so viral invasion would not lead to viral copies. Answer D is incorrect because modification reduces retroviruses ability to replicate.

Deck 26: Gene Therapy