why is a cDNA inserted into lyphocytes for curing ada deficiency? what if a normal dna is inserted and not a cDNA?
Dear student,
Adenosine deaminase (ADA) is an enzyme crucial for immune system. Its deficiency is caused due to the deletion of the gene coding for adenosine deaminase. The gene codes for the enzyme adenosine deaminase (ADA). Without this enzyme, the body is unable to break down a toxic substance called deoxyadenosine. The toxin builds up and destroys infection-fighting immune cells called T and B lymphocytes.
Lymphocytes isolated from patient’s blood are cultured in-vitro. Functional ADA cDNA are then introduced into the cultured lymphocytes. These lymphocytes are returned back to the patient’s body. cDNA are inserted because it can be easily cloned and large number of copies can be produced so that enzyme ADA can be produced in large amount which do not contain introns and the process of splicing which is a time taking event is not required. cDNA only contains exons which can be transcribed without splicing and finally translated to produce adenosine deaminase enzyme.
If normal DNA is inserted it can not be easily cloned and requirement of the enzyme can not be fulfilled.
Lymphocytes are not immortal. Therefore, repeated infusion of genetically engineered lymphocytes is required and hence it is not a permanent treatment. If the gene producing Adenosine Deaminase is isolated from bone marrow and is introduced into the cells of an organism in early embryonic cells, it can be a permanent cure of ADA deficiency.
Regards
Adenosine deaminase (ADA) is an enzyme crucial for immune system. Its deficiency is caused due to the deletion of the gene coding for adenosine deaminase. The gene codes for the enzyme adenosine deaminase (ADA). Without this enzyme, the body is unable to break down a toxic substance called deoxyadenosine. The toxin builds up and destroys infection-fighting immune cells called T and B lymphocytes.
Lymphocytes isolated from patient’s blood are cultured in-vitro. Functional ADA cDNA are then introduced into the cultured lymphocytes. These lymphocytes are returned back to the patient’s body. cDNA are inserted because it can be easily cloned and large number of copies can be produced so that enzyme ADA can be produced in large amount which do not contain introns and the process of splicing which is a time taking event is not required. cDNA only contains exons which can be transcribed without splicing and finally translated to produce adenosine deaminase enzyme.
If normal DNA is inserted it can not be easily cloned and requirement of the enzyme can not be fulfilled.
Lymphocytes are not immortal. Therefore, repeated infusion of genetically engineered lymphocytes is required and hence it is not a permanent treatment. If the gene producing Adenosine Deaminase is isolated from bone marrow and is introduced into the cells of an organism in early embryonic cells, it can be a permanent cure of ADA deficiency.
Regards