Types of gene therapy

Gene therapy started initially as gene injection. This involved several strategies for incorporating genes into somatic cells or into early embryos. When an organism incorporates an alien gene it is then said to be transgenic. Genes can be used to treat congenital abnormalities which are caused by mutation through the replacement by cDNA or polynucleotide sequences.

Another strategy is to induce a suppressor mutation. This is done with the use of tRNA which then suppresses the mutation existing in the gene to be expressed. The change which occurs in the tRNA helps to code for the normal amino acid rather than the abnormal one and hence cures the condition permanently.

Strategies for incorporating genes into cells

  1. The use of microcells. This is the incorporation of DNA molecules into the chromosomes, which are the microcells. The microcells act as vectors for the replication of genes. Microcells are chromosomes which have picked out at metaphase  of dividing cells.
  2. Role of calcium precipitation. Cells to be replaced with genes are taken from the body and placed in a test tube to which calcium salt has been added. Calcium breaks down the cell wall  and allows the gene to be incorporated into the cell. The cells are then grown in culture to increass their number. They will replicate the gene that has been incorporated and they are then replaced into the body. This strategy is vital for the treatment strategy of the hemoglobinopathies, since red cells which are immature can be injected with normal genes and replaced into the body. The strategy is also vital in replacing diseased endocrine cells.
  3. Direct intranuclear injection. Using micropipette methods, a gene can be directly injected into the nucleus of a cell for its incorporation thereby bypassing cell membrane and the need to provide calcium for the purpose of transport across the cell membrane. This strategy is often used for injecting early embryonal cell at the zygotic stage. At the stage of morula the method may change to the incorporation of genes using calcium for transport across cells since this must involve many cells at the same time.
  4. Use of viral carriage:  Certain retroviruses and others such as SV-40 (simian virus -40) can be used for carrying genes into tissues. The virus is injected into the cell and the cell is grown in culture. Once the virus is incorporated into the genome of the cell it releases its contained gene which may form a provirus in that genome. With the culture of the cell, several copies of the cell containing the virus are made and then reinjected into the body to influence either somatic or germ cell.

Other modern methods include

  • Immunpotentiation,
  • Mutation compensation,
  • Molecular chemotherapy (suicide gene therapy), 
  • Viral mediated oncolysis,
  • Antiangiogenic therapy.



Cell types

Organ integration



Chemical Pathology




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