The United Nations Convention on Biological Diversity defines biotechnology as:
"Any technological application that uses biological systems, living organisms, or derivatives thereof, to make or modify products or processes for specific use."

In other terms: "Application of scientific and technical advances in life science to develop commercial products" is biotechnology.

Biotechnology in short biotech is a field of applied biology that involves the use of living organisms and bioprocesses in engineering, technology, medicine. Genetic engineering as well as cell- and tissue culture like terms are also included in this area. This is modification of living organisms according to human purposes like domestication of animals, cultivation of plants, and "improvements" to these through breeding programs including artificial selection and hybridization.

Gene therapy

Genes are carried on chromosomes, are specific sequences of bases that encode instructions on how to make proteins. It is the proteins that controls most life functions and even build up the majority of cellular structures. When genes are changed, encoded proteins are unable to perform their normal functions, genetic disorders can happen.

Gene therapy is a technique for correcting defective genes responsible for disease development. It includes following approaches.

Most commonly a normal gene may be inserted into a nonspecific location within the genome to replace a nonfunctional gene.

The abnormal gene is repaired through selective reverse mutation and returns the gene to its normal function.

An abnormal gene could be changed for a normal gene through homologous recombination.
The regulation (the degree to which a gene is turned on or off) of a particular gene could be altered.

How it works?

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

Target cells such as liver or lung cells are infected with the viral vector. The vector then unloads its genetic material containing the therapeutic human gene into the target cell. The generation of a functional protein product from the therapeutic gene restores the target cell to a normal state.

Gene Therapy vectors

Retroviruses - Viruses that can create double-stranded DNA copies of their RNA genomes. Copies of its genome can be integrated into the chromosomes of host cells. Ex.Human immunodeficiency virus (HIV).

Adenoviruses - Viruses with double-stranded DNA causing respiratory, intestinal, and eye infections in humans.Ex. virus that causes the common cold.

Adeno-associated viruses - Single-stranded DNA viruses that can insert their genetic material at a specific site on chromosome 19.

Herpes simplex viruses - Double-stranded DNA viruses that infect particular cells called neurons. Herpes simplex virus type 1 is a common human pathogen that causes cold sores.
Other than virus-mediated approaches, there are several nonviral options also like direct introduction of therapeutic DNA into target cells. But it is limited because it can be used only with certain tissues and requires large amounts of DNA. Other process involves the creation of an artificial lipid sphere with an aqueous core. This liposome carrying therapeutic DNA, is capable of passing the DNA through the target cell's membrane. Therapeutic DNA also can also be inserted inside target cells by chemically linking the DNA to a molecule that will bind to special cell receptors, but less effective than other options.

Gene therapy may be used for treating, or even curing, genetic and acquired diseases like cancer and AIDS by using normal genes to supplement or replace defective genes or to bolster a normal function such as immunity. It can be used to target somatic cells (i.e., those of the body) or gametes (i.e., egg and sperm) cells. In Somatic Gene Therapy, the genome of the recipient is changed without passing in the next generation in Gamete Gene Therapy, the egg and sperm cells of the parents are changed for the purpose of passing on the changes to their offspring.

There are basically two ways of implementing a gene therapy treatment:

• Ex vivo, which means "outside the body" - Cells from the patient's blood or bone marrow are removed and cultured in the laboratory. Next they are exposed to a virus having the desired gene. The virus enters the cells, and the desired gene is incorporated in the DNA of the cells. Now the cells are allowed to grow in the laboratory before being returned to the patient by injection into a vein.
• In vivo, which means "inside the body" - Cells are not removed from the patient's body and the vectors are used to deliver the desired gene to cells in the patient's body.

Problems in Gene Therapy

Gene therapy faces many hurdles before it can be practically applicable for treating diseases. Some of these are as follows:

Viral vectors create problems - Viruses, present a variety of potential problems to the patient --toxicity, immune and inflammatory responses, and gene control and targeting issues. There is always a chance for the viral vector, to recover its ability to cause disease inside the patient.

Limited knowledge of the functions of genes - Currently the functions of only a few genes are known. Hence, gene therapy can cover only some genes that cause a particular disease. Other thing is that genes have more than one function so there is uncertainty as to whether replacing such genes is indeed desirable.

Multigene disorders and effect of environment - Most genetic disorders involve more than one gene. Mostly diseases involve the interaction of several genes and the environment. For example, many people with cancer not only inherit the disease gene for the disorder, but may have also failed to inherit specific tumor suppressor genes. Diet, exercise, smoking and other environmental factors may have also contributed to their disease.

High costs - Gene therapy is somewhat new and at an experimental stage so proved to be an expensive treatment. That is why current studies are focused on illnesses commonly found in developed countries, where people can easily afford the treatment. Developing countries can take advantage of this technology after some time but not yet.

Gene therapy is of short span - Cells containing the therapeutic DNA must be long-lived and stable. Problems with integrating therapeutic DNA into the genome and the rapidly dividing nature of many cells cause gene therapy short term beneficial. Patients will have to go multiple rounds of gene therapy.

Immune Response - The immune system is designed to attack the invader. The risk of stimulating the immune system reduces gene therapy effectiveness. Also, the immune system's enhanced response to invaders makes it difficult for gene therapy to be repeated in patients.

Gene delivery tools - Genes are inserted in the body with the help of carriers known as vectors. The most common vectors now are viruses, which are also pathogenic. Scientists manipulate the genome of the virus by removing the disease-causing genes and inserting the therapeutic genes. Though viruses are effective, they can cause problems like toxicity, immune and inflammatory responses, and gene control and targeting issues. Also, for gene therapy to provide permanent therapeutic effects, the introduced gene needs to be integrated within the host cell's genome. Some viral vectors work this in a random fashion, which can introduce other problems such as disruption of an endogenous host gene.

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