2 The main advances in medicine Improved sanitation systemsSurgery with anesthesiaVaccines and antibioticsAnd the fourth will be Gene Therapy
3 What is gene therapy?The selective delivery of genes into a patients cellscreate missing proteinsreplace defective disease causing genesOver 4,000 conditions are caused by damage to a single gene, many others by several genes
4 Gene therapy techinques Ex-vivo “outside the body”adding blood cells with new DNA to the blood streambut has a limited time spanUsing bacteria like E.coli to produce billions of copies of a human geneUsing viruses to carry the gene to specific cells in the body
5 What do you need? A cutting enzyme called a Restriction enzyme It cuts foreign DNA that enter bacteria, e.g. Eco. R1A circular DNA molecule from a bacteria called aPlasmidThe E. coli bacteria has dozens of different plasmidsA section of the human DNA containing the gene you needAn enzyme to join the bacterial DNA and human DNA calledligase
6 Restriction Enzymes Found in many bacteria A defense mechanism which cuts foreign DNAThe DNA is not cut randomly, but at specific sequences calledRecognition sequencesThe restriction enzyme Eco.R1 found in strain C, E. coli bacteriaThey don’t make straight cuts, but produce sticky endsThese sticky ends can rejoin by forming hydrogen bonds and the sugar-phosphates rejoining with the help of the enzyme ligaseThe DNA produced by restriction enzymes cutting is called gDNAWe know of 200 different restriction enzymes
7 PlasmidsThe Plasmid pSC101 was isolated from E. coli. It is useful for gene therapy because it has only one sequence of GATTC in its entire moleculePlasmids can be used to replicate DNA segments of up to 4,000 base pairs in lengthFor longer length viruses must be used.
8 Using Bacterial Plasmid Cut the Bacterial Plasmid using restriction enzyme called Eco R1
10 This produces a hole in the circular Plasmid DNA Eco. R1 only cuts at the sequence GAATTCThis produces two identical ends
11 PlasmidAlso treat human DNA with Eco.R1 and you get a section of DNA containing the gene you want with two complementary ends as well!Short sequence of DNA with sticky ends approaches a Plasmid.Human DNA
13 Bacterial DNAHuman DNAThe newly completed piece of DNA is calledRecombinant DNA
14 Using this Recombinant DNA Gene cloning can now be used to produce millions of copies
15 A Plasmid with human DNA is put back into a E. coli The bacteria expresses the DNA.The bacteria then divides to produce millions of copies bacteria and human gene.
16 A Plasmid cut by a restriction enzyme Foreign DNA spliced into Plasmid byPlasmid enters bacterial cellSegment of DNA approachesDNA ligase joins phosphates and sugars
17 Using virusesViruses can be used to transfer large pieces of human DNA to a location in the Human body.Viruses are made up of a molecule of nucleic acid and a protein coat.Their nucleic acid codes for protein coats, replication, enzymes to break-in and out of particular cells.You remove the part of the nucleic acid that does not code for the above functions and add foreign DNA.The virus can then be put into the blood stream and it will enter the cell it is designed to attack and transfer its code into that cell.
18 Some current uses of gene therapy and later cosmetic uses Some current uses & trials of gene therapyIntroduction of genes for new blood vessels for clogged arteriesIntroduction of genes into the blood stream that interferes with the replication of HIVHuman growth hormone for DwarfismInsulin productionGlowing miceReplacing the cytoplasm in eggs to produce healthier eggsSome current uses of gene therapy and later cosmetic uses
19 The future?Injecting genes into the blood stream which are then carried to the target cells by viral carriers where they unload their genetic material.This is then used by the body to produce proteins that fight the disease.For the next decade gene therapy will only be used on somatic cells (only effect the patient and not their offspring)You and bioethicists will have to decide the future!