Question

What is DNA deficiency? Which disease is associated with it?

Answer 1

Hint: DNA deficiency is the lack of DNA in the body. There are various reasons for the inhibition of the synthesis of DNA. Some diseases can be caused due to faulty metabolism and synthesis of DNA.

Complete step by step answer:
- DNA deficiency is the lack or absence of genes in the cell, which can be harmful to the body and can even result in death. Gene therapy is being sought after to correct this anomaly.
- Severe combined immunodeficiency is an example of a deficiency of a gene causing disease. SCID is caused due to various factors. One of the common reasons for SCID is the deletion of the ADA (adenosine deaminase) gene which is essential for the metabolism of the purines in the body. Lack of this enzyme causes accumulation of deoxyadenosine triphosphate (dATP) a purine nucleotide, which will inhibit the activity of ribonucleotide reductase, an enzyme that reduces ribonucleotides to generate deoxyribonucleotides.

Additional Information:
- The effectiveness of the immune system depends on the spread of lymphocytes in the body, which is not possible due to the lack of synthesis of nucleotides (dNTPs). This leads to defective B-cells and T-cells and a severely compromised immune system, leaving the body susceptive to a spectrum of diseases and disorders.
- SCID is also caused due to mutations in the purine nucleoside phosphorylase (PNP) gene, which encodes the key enzyme PNP in the purine salvage pathway. Without PNP, dGTP accumulates and hampers DNA synthesis.
- SCID is characterized by chronic bacterial, fungal, and viral infections, coupled with lung disease. Most children affected die within the first few years of their life unless they undergo hematopoietic stem cell transplants or gene therapy.
 - Gene therapy is used for the treatment of SCID which is successful in some cases. In some children, ADA deficiency can be cured to ameliorate SCID by bone marrow transplantation or by enzyme replacement therapy in which functional ADA is given to the patient by injection.

Note:
- SCID is also known as bubble baby disease as the person suffering from it has to live in a completely sterile environment as they are completely vulnerable to any infectious disease.
- Other names of the disease are Alymphocytosis, Glanzmann–Riniker syndrome, Severe mixed immunodeficiency syndrome, and Thymic alymphoplasia.