Gene therapy –

• Gene therapy is a collection of methods that allows correction of gene defects, diagnosed in a child or embryo.
• By insertion of normal genes,the defective mutant allele of the genes of the genes are replaced and non – functional gene is compensated.
• For the first time in 1990 , M. blease and W.F. Andrescose of National institute of Health, attempted gene therapy on a 4 year old girl with adenosine deaminase (ADA) deficiency.
• ADA is caused due to deletion of gene for adenosine deaminase.
• In some cases, it can be cured by bone marrow transplantation and enzyme replacement therapy but it is not fully curative.
• Lymphocytes from the patient’s blood were grown in a culture and functional ADA, cDNA was introduced in these lymphocytes using a retroviral vector.
• The lymphocytes were transferred into the patient’s body, periodic infusion of such genetically engineered lymphocytes is done because these cells are mortal.
• For permanent cure, gene isolated from the bone marrow cells producing ADA , at early embryonic stage can be a possible cure.
• Other diseases like cystic fibrosis, haemophilia, cancer, parkinson’s etc.are also treated by gene therapy.

Molecular diagnosis –

Early detection of disease is not possible by conventional diagnosis methods.

Some techniques used for early diagnosis are :-

a) Polymerase chain reaction –

• Low concentration of the pathogen in the body does not allow its detection.
• The nuclear acid of the pathogen ( bacteria or virus ) is amplified by PCR for its detection.
• It is being used for detection of HIV in suspended AIDS patients and genetic mutations in suspected cancer patients.

b) Recombinant DNA technology –

• A single stranded DNA or RNA tagged with a radioactive molecule is called probe.
• In the method, a probe is allowed to hybridise to its complementary DNA in the clone of cells.
• The cells are then detected by autoradiography.
• The cells with mutated gene will not be observed on the photographic film because the probe was not complementary to the mutated gene.

c) Enzyme linked immune – sorbent assay (ELISA) –

• It is based on the principle of antigen- antibody interaction.
• Either the presence of antigens ( proteins , glycoprotein , etc. ) are detected or the antibodies produced against the pathogens are detected.

d) Stem cell technology –

• Stem cells are undifferentiated biological cells. These can differentiate into specialized cells and can divide to produce more stems cells.
• Stem cells are found in multicellular organisms.
• Adult stem cells are used in medical therapies, for example, in bone marrow transplantation.
• Stem cells can also be taken from umbilical cord just after birth.