Question 1

In substrate reduction therapy,a drug taken by mouth decreases the amounts of the molecule on which a deficient enzyme acts.

Accepted Answer

Substrate reduction therapy involves reducing the amount of the substrate, or molecule, on which a deficient enzyme acts. This can be achieved through the use of drugs taken by mouth that decrease the production or accumulation of the substrate, thus reducing the burden on the deficient enzyme and potentially alleviating symptoms of the associated genetic disorder.

Question 2

Which is an example of a germline gene therapy?

Accepted Answer

Germline gene therapy involves altering the genes in the germ cells (sperm or eggs) or early embryos, which can be passed on to future generations. A transgenic plant or animal is an example of germline modification, as it involves altering the genetic makeup at the embryonic stage.

Question 3

A serious limitation of using a retrovirus as a vector for gene therapy is that

Accepted Answer

Retroviruses have the potential to insert their genetic material into the host genome, potentially disrupting normal gene function. If a retrovirus inserts itself into a proto-oncogene, it may activate it, leading to uncontrolled cell growth and potentially causing cancer. This risk limits the use of retroviruses as vectors for gene therapy.

Question 4

Leber congenital amaurosis type 2 has been successfully treated using gene therapy.

Accepted Answer

Leber congenital amaurosis type 2 has been successfully treated using gene therapy. In 2017, the FDA approved the first gene therapy to treat this condition, called Luxturna.

Question 5

Performing gene therapy on somatic cells removed from the body and then returning these cells to the body is called _____ gene therapy.

Accepted Answer

The term for performing gene therapy on somatic cells removed from the body and then returning these cells to the body is ex vivo gene therapy. In vivo gene therapy is performed directly within the body, in situ gene therapy is performed in the original location of the cells or tissues, and in vitro gene therapy is performed entirely outside the body in a laboratory setting. Therefore, the best choice is D for ex vivo gene therapy.

Question 6

Reginald receives a stem cell transplant to treat a blood cancer,multiple myeloma.His treatment is an example of

Accepted Answer

Reginald's treatment is an example of somatic gene therapy, which aims to alter or replace non-reproductive cells in the patient's body to treat a genetic disease or disorder. Stem cell transplant involves replacing the patient's defective or cancerous blood cells with healthy stem cells from a donor. Germline gene therapy aims to alter the genes in reproductive cells and pass them onto future generations, whereas heritable gene therapy involves altering the genes in reproductive cells that can be passed onto offspring. In vitro fertilization is a fertility treatment that involves fertilizing an egg outside the body and then implanting it into the uterus.

Question 7

A patient received bone marrow modified by an adeno-associated virus (AAV)carrying a human gene that encodes an enzyme her body could not make.This is an example of

Accepted Answer

This is an example of somatic gene therapy because the modification only took place in the patient's bone marrow cells and did not affect their germ cells (eggs/sperm) which could pass on the modified gene to future generations. The use of adeno-associated virus (AAV) also indicates that this therapy involves gene delivery using a non-integrating viral vector, unlike retroviral gene therapy which uses integrating retroviruses. Protein therapy involves administration of proteins directly rather than altering genes, while germline gene therapy involves modifying germ cells to pass on the changes to future generations (which was not done in this case).

Question 8

Which of the following would provide the longest lasting treatment for Leber's congenital amaurosis II?

Accepted Answer

Leber's congenital amaurosis II is caused by a mutation in the RPE65 gene, which regulates the production of a protein essential for vision. Injecting adeno-associated virus carrying a wild type version of the RPE65 gene into affected cells of the retina is a gene therapy that is safe and effective in treating LCA2, providing long-term benefits. The other options listed do not directly address the genetic mutation causing the disease and are not effective treatments for LCA2.

Question 9

Using gene therapy to correct ornithine transcarbamylase deficiency (OTC)would prevent buildup of _____ in the blood.

Accepted Answer

Ornithine transcarbamylase deficiency results in the accumulation of ammonia in the blood, leading to hyperammonemia. Gene therapy aimed at correcting this deficiency would prevent the buildup of ammonia, and thereby correct this metabolic disorder.

Question 10

Repurposing a drug is much more economical than developing a new one.

Accepted Answer

Repurposing a drug involves using an already existing drug for a different medical condition than what it was originally intended for. It is much more economical than developing a new drug from scratch, as the drug has already undergone regulatory approval and safety testing. Additionally, repurposing a drug saves time and resources that would otherwise be spent on the lengthy and expensive drug development process.

Question 11

Which of the following is a vector used to deliver genes in human gene therapy?

Accepted Answer

Adeno-associated virus (AAV) is commonly used as a vector in human gene therapy due to its low pathogenicity and ability to stably integrate genetic material into host cells. Parvovirus and Rabies virus are not commonly used in human gene therapy, and E.coli is a bacterium and not a virus, making it unsuitable as a vector for gene therapy.

Question 12

Introducing a gene in a liposome to carry DNA across the plasma membrane is a(n)_____ gene therapy.

Accepted Answer

In vivo gene therapy involves introducing a therapeutic gene directly into the patient's body, and liposomes are commonly used as delivery vehicles for these genes. The other options are not relevant to the use of liposomes as a delivery mechanism.

Question 13

Many children born with ornithine transcarbamylase deficiency (OTC)die within seventy-two hours of birth.Jesse Gelsinger was not diagnosed with OTC until he was two because _____ and therefore his symptoms were milder.

Accepted Answer

Jesse Gelsinger's milder symptoms suggest that he was a mosaic, meaning that not all of his cells carried the defective gene. This is possible because OTC follows an X-linked dominant pattern of inheritance, so males can be affected if their mother passes on the defective X chromosome. If Jesse had inherited the defective X chromosome in all of his cells, he likely would have presented with more severe symptoms, possibly leading to an earlier diagnosis. Autosomal recessive inheritance, X-inactivation in males, and parental imprinting are not applicable to the inheritance pattern of OTC.

Question 14

Which of the following would provide the longest lasting treatment for adenosine deaminase (ADA)deficiency?

Accepted Answer

Receiving white blood cells genetically modified to carry functional ADA genes would provide the longest lasting treatment for ADA deficiency as they would continuously produce the missing enzyme. Options A, B, and D would provide temporary relief but would not address the underlying genetic defect causing the deficiency.

Question 15

Germline gene therapy would correct a genetic defect in

Accepted Answer

Germline gene therapy targets the reproductive cells (sperm or eggs), meaning that the genetic correction is passed on to all future descendants of the affected individual.

Question 16

Adenosine deaminase (ADA)deficiency results in

Accepted Answer

Adenosine deaminase (ADA) deficiency leads to severe combined immune deficiency (SCID), a condition in which the immune system is severely compromised, leading to susceptibility to infections. There is no direct link between ADA deficiency and hereditary emphysema, neurotransmitter imbalances or chronic myelogenous leukemia.

Question 17

A nasal spray for cystic fibrosis patients,which contains adenovirus particles carrying a normal human CFTR gene,is an example of

Accepted Answer

In vivo gene therapy involves the direct delivery of therapeutic genetic material into the patient's body to correct a genetic defect, which is the case here with the delivery of adenovirus particles carrying the CFTR gene via a nasal spray.

Question 18

Tyrone has Gaucher disease.He receives recombinant glucocerebrosidase every other week in an infusion to prevent the symptoms.This treatment is an example of

Accepted Answer

Enzyme replacement therapy involves infusing a patient with a functional enzyme to replace the deficient or dysfunctional enzyme in their body. In this case, Tyrone receives recombinant glucocerebrosidase to replace the deficient enzyme responsible for Gaucher disease.

Question 19

Pharmacological chaperone therapy

Accepted Answer

Pharmacological chaperone therapy is a treatment that involves using small molecules to restore proper folding to a misfolded protein. This restores the function of the protein and can be used to treat diseases caused by protein misfolding, such as cystic fibrosis and Gaucher disease. Answers B, C, and D are incorrect because they do not accurately describe pharmacological chaperone therapy.

Question 20

Nonheritable gene therapy is performed on _____ cells.

Accepted Answer

Nonheritable gene therapy is performed on somatic cells, which are cells that make up the body but do not contribute to producing offspring. This type of therapy aims to treat genetic disorders or diseases by targeting specific cells and tissues in the body. The changes made through nonheritable gene therapy are not passed on to future generations because they do not affect the germline cells (sperm and egg cells).

Quiz 20: Genetic Testing and Treatment