Genomics, gene editing and cell therapy

Prelims and Mains

A gene is a stretch of DNA whose sequence of bases spells out one protein, and Mendel's rules have each of its two copies passed on unchanged and independently. A map of the chemical marks carried on the DNA of two mouse strains has now turned up more than 500 instances of inheritance those rules do not predict.

• A gene is felt only when it is read: transcription copies it into messenger ribonucleic acid (mRNA), and translation builds the protein from that copy.
• The marks mapped were DNA methylation, read across the two strains by nanopore sequencing.
• In some regions the methylation depended on the mouse's sex.
• Marks could copy from one gene copy to the other.
• Similar mechanisms may explain human conditions that resist standard genetic analysis.

Prelims and Mains

Every proven use replaces a tissue with the same tissue, and each took decades of trials to reach the clinic. The list is short, and a good deal shorter than what clinics advertise.

• Haematopoietic stem cell transplantation, the bone marrow transplant, treats leukaemia, lymphoma, thalassaemia and aplastic anaemia.
• Limbal stem cells from the eye restore a cornea scarred by chemical burns.
• Cultured skin cells are grafted onto severe burns.
• Other conditions, neurological and degenerative disease among them, remain investigational, for an approved clinical trial only.
• No whole organ has yet been grown from stem cells for human transplant.

Prelims and Mains

Research and the products sold as treatment fall to different regulators. The newest guidelines are a layer added on top of that division rather than a replacement for it.

• The National Stem Cell Research Regulation Committee oversees research using minimally manipulated stem cells.
• The Central Drugs Standard Control Organisation (CDSCO) regulates stem cell products as drugs, under the New Drugs and Clinical Trials Rules, 2019.
• The Health Ministry's Centre for Evidence Based Guidelines issued guidelines on stem cell therapy and regenerative medicine for 2025 to 2026.
• They join the National Guidelines for Stem Cell Research 2017, the gene therapy guidelines 2019, the haematopoietic cell transplantation guidelines 2021 and the cord blood banking guidelines 2023.
• India's first in human gene therapy trial was run by the Centre for Stem Cell Research with Christian Medical College, Vellore.

Prelims and Mains

Base editing, developed in 2016, converts one DNA letter into another without cutting both strands, unlike CRISPR-Cas9, so it should cause fewer unintended changes. Delivery to the brain needs large doses of adeno associated viruses, which can provoke a severe immune reaction.

Mains

A gene drive is engineered DNA that passes to far more than half of an organism's offspring and so spreads through a wild population, proposed for collapsing mosquito populations and opposed for effects that cannot be reversed.