10 - Gene Therapy

Question 1

Gene therapy

Answer 1

A collection of techniques for
correcting a defective gene problem.

Question 2

Examples of a mutated gene (germline or somatic) that may lead to a protein that cannot carry out its normal function

Answer 2

• Duchenne Muscular Dystrophy (DMD)
• Severe Combined Immunodeficiency Disease (X SCID)
• Sickle Cell Disease (SCD)

Question 3

Common Approaches to Gene Therapy

Answer 3

• A normal gene copy may be inserted into a nonspecific location within the genome to replace a nonfunctional gene. (most common)
• An abnormal gene could be swapped for a normal gene through homologous recombination.
• The abnormal gene could be repaired through selective reverse mutation, which returns the gene to its normal function.
• The regulation of a particular gene could be altered.

Question 4

Viral vectors in Gene therapy

Answer 4

• Adenoviruses
• Adeno-associated viruses
• Herpes simplex virus
• Retroviruses

Question 5

Adenovirus

Answer 5

• A class of viruses with double- stranded DNA genomes that cause respiratory, intestinal, and eye infections in humans
• Causes common cold

Question 6

Adeno-associated viruses

Answer 6

A class of small, single-stranded DNA viruses that can insert their genetic material at a specific site on chromosome 19.

Question 7

Herpes simplex virus

Answer 7

• A class of double-stranded DNA viruses that infect neurons
• HSV type 1 is a common human pathogen that causes cold sores.

Question 8

Retroviruses

Answer 8

• A class of viruses that can create double-stranded DNA copies of their RNA genomes.
• These copies of its genome can be integrated into the chromosomes of host cells
• e.g. Human immunodeficiency virus (HIV)

Question 9

Correction of X-SCID approach

Answer 9

Ex-vivo correction of X-SCID genes in bone marrow cells

Question 10

Correction of X-SCID technique

Answer 10

• Bone marrow cells isolated from patient
• Bone marrow cells transfected in vitro with recombinant retrovirus engineered to carry “normal” versions of the X-SCID defective genes
• The retrovirally transfected genes are tested for integration and expression in the bone marrow cells
• The transformed bone marrow cells are returned to the patient

Question 11

Non viral delivery of gene therapy

Answer 11

• DNA transfer by physical means
• Liposomal DNA delivery
• Whole cell transplantation
• (Mammalian expression) plasmids

Question 12

DNA transfer by physical means

Answer 12

• Direct injection
• Electroporation
• Gene gun