Topic Stem Cell and Gene Therapy Essay - Main Points!

Q) Discuss the use of viral and non-viral delivery systems in gene therapy

Main points
Key idea:	What is gene therapy
· Technique for introducing normal copy of the gene into patient suffering fr a genetic disease · Normal gene or allele produces functional proteins; hence restores normal functions of target cells · Two types of delivery sys – (i) viral (ii) non-viral delivery sys
Key idea:	Viral delivery system
· Viral delivery sys: viruses genetically modified (GM) to carry normal human gene · GM viruses then infect target cells - introduce normal gene into them
Key idea:	Named example : (1) Retroviruses
· E.g. Retroviruses carry normal gene coding for adenosine deaminase (ADA) to actively dividing bl stem cells · Adv: ability to integrate the normal gene into lymphocyte chrom for long term treatment of patients w ADA-SCID
Key idea:	Named example : (2) Adenoviruses
· E.g. Adenoviruses carry normal gene coding for cystic fibrosis transmembrane conductance regulator protein (CFTR) to epithelial cells of airways + gut · Adv: treat patients with cystic fibrosis
Key idea:	Non-viral delivery systems
· E.g. Gene gun - introduce DNA directly into target cells · E.g. Liposome - DNA is packaged into synthetic vesicles (liposomes) made up of a lipid bilayer struc which · may be further coated w carbohydrates or peptide chains that bind to specific receptors on surface of target cells
Key idea:	Liposome - process of gene introduction
· Liposomes can introduce normal gene into target cells either by (i) electroporation or by (ii) binding to surf receptors on target cells  · Liposome fuses w cell membrane, then introduces gene into target cell
Comments: (i) Visualize the answer with the aid of a labelled diagram. (ii) Verbalize the answer + write down the main points w/o referring to the answer (use abbreviations) (iii) Read again within the next 24h & once more within 72h (do not spend more than 10min) (iv) To gain maximum marks, explain the term gene therapy before explaining the two delivery systems. (v) Whenever possible, students should use named examples to support their answers (vi) The selection of the type of virus (e.g. adenovirus and retrovirus) depends on the type of cells being targeted. For example, adenoviruses (which are flu viruses) are effective in targeting the slow or non-dividing epithelial cells of the airways and gut. Retroviruses are effective in targeting actively dividing cells