2. In most gene therapy studies, a "normal" gene is inserted into the genome to replace an "abnormal," disease-causing gene. A carrier molecule called a vector must be used to deliver the therapeutic gene to the patient's target cells. Currently, the most common vector is a virus that has been genetically altered to carry normal human DNA

3. Retroviruses - Retroviruses are known to lead to certain types of cancers in both humans and animals, as well as a range of viral infections. Human Immunodeficiency Virus (HIV), the virus that causes Acquired Immune Deficiency Syndrome (AIDS), is one example of a retrovirus. Adenoviruses - A class of viruses with double-stranded DNA genomes that cause respiratory, intestinal, and eye infections in humans. The virus that causes the common cold is an adenovirus. Adeno-associated viruses - A class of small, single-stranded DNA viruses that can insert their genetic material at a specific site on chromosome 19. Herpes simplex viruses - A class of double-stranded DNA viruses that infect a particular cell type, neurons. Herpes simplex virus type 1 is a common human pathogen that causes cold sores.HIVImmune Deficiency

4. Ethical considerations for using Gene therapy. People have had to deal with genetic inequality as a fact of life. With the advent of gene therapy, this may no longer be the case for some people. Most people feel that it is okay to use gene therapy to treat human genetic diseases. Somewhat surprisingly. Some individuals, however, are concerned that the technique may be used for "treatment" of genetic "disorders" other than diseases. Because many people are concerned about the safety of gene therapy, a special committee of the National Academy of Science was created to look into the consequences of releasing rDNA engineered organisms into the environment. The committee concluded that "there is no evidence that unique hazards exist either in the use of rDNA technique or in the transfer of genes between unrelated organisms," and that, "the risks associated with the introduction of rDNA engineered organisms are the same kind as those associated with the introduction of unmodified organisms.

7. The use of gene therapy has five basic steps, and there are a variety of methods to achieve each step. · Step 1: The gene coding for the desired protein is isolated.

8. · Step 2: The gene is delivered to a target cell by means of a vector. This vector carries the gene and gets it into the cell.

9. · Step 3: The cell integrates this gene and begins to produce DNA and RNA coding for the protein.

10. · Step 4: The protein is made by the cell.

11. · Step 5: This protein acts inside the cell or is released into the environment and then stimulates the desired action such as spinal fusion or disc regeneration.