Biotechnology and its Applications Test - 8

As a first step towards gene therapy, lymphocytes from the blood of the patient are grown in a culture outside the body. A functional ADA cDNA is then introduced into the lymphocytes using a retroviral vector, which are subsequently returned to the patient.

Adenosine deaminase deficiency (ADA) is an inherited condition that affects the immune system and typically leads to severe combined immunodeficiency (SCID). People with SCID have a reduced or absent immune response which leaves them vulnerable to frequent bacterial, viral, and fungal infections. Most people affected by ADA develop symptoms of the condition before 6 months of age.

ADA is caused by changes (mutations) in the ADA gene and is inherited in an autosomal recessive manner.

The most effective treatment is transplantation of blood-forming stem cells from the bone marrow of a healthy person. Bone marrow is responsible for blood formation.

ELISA works on the principle of antibody-antigen interaction. In case of low concentration of pathogen it can give false test in the beginning of infection.

Post-transcriptional gene silencing (PTGS) in plants is an RNA-degradation mechanism that shows similarities to RNA interference (RNAi) in animals. Indeed, both involve double-stranded RNA (dsRNA), spread within the organism from a localised initiating area, correlate with the accumulation of small interfering RNA (siRNA) and require putative RNA-dependent RNA polymerases, RNA helicases and proteins of unknown functions containing PAZ and Piwi domains It prevents the expression of mRNA or silence the gene after transcription.

The most important application of animal cell cultures is the production of a wide range of commercial compounds for medical and pharma­ceutical use.

Monkey kidney or chick embryo cells or recently human diploid cells are in use for the production of vaccines. The vaccine manufacture in animal cell cultures is rather complex with risk of contamination, and safety aspect. For these reasons, production of vaccines by recombinant DNA technology employing bacteria or yeasts is preferred.

Cellular Totipotency is the ability of a single cell to produce all cell types and to organise them into an entire organism when cultured in a suitable culture medium at appropriate temperature and aeration conditions. Spores and Zygote are examples of totipotent cells.

Sandwich ELISA is a less common variant of ELISA, but is highly efficient in sample antigen detection. Moreover, many commercial ELISA pair sets are built on this sanwich ELISA.

The sandwich ELISA quantify antigens between two layers of antibodies (i.e. capture and detection antibody). The antigen to be measured must contain at least two antigenic epitope capable of binding to antibody, since at least two antibodies act in the sandwich

In mammals, including humans, insulin is synthesised as a prohormone (like a pro-enzyme, the pro-hormone also needs to be processed before it becomes a fully mature and functional hormone) which contains an extra stretch called the C peptide. This C peptide is not present in the mature insulin and is removed during maturation into insulin.

The blue-white screen is a screening technique that allows for the rapid and convenient detection of recombinant bacteria in vector-based molecular cloning experiments. DNA of interest is ligated into a vector.

The method is based on the principle of α-complementation of the β-galactosidase gene. This phenomenon of α-complementation was first demonstrated in work done by Agnes Ullmann in the laboratory of François Jacob and Jacques Monod, where the function of an inactive mutant β-galactosidase with deleted sequence was shown to be rescued by a fragment of β-galactosidase in which that same sequence, the α-donor peptide, is still intact.

A single stranded DNA or RNA, tagged with a radioactive molecule (probe) is allowed to hybridise to its complementary DNA in a clone of cells followed by detection using autoradiography. The clone having the mutated gene will hence not appear on the photographic film, because the probe will not have complimentarity with the mutated gene.

ELISA is based on principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens or by detecting the antibodies synthesized in the body.