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Molecular biology: DNA and proteins
Four findings share one chain of ideas: a gene is copied, read and folded into a protein whose shape is its function. A study of DNA replication, a map of inherited chemical marks in mice, an artificial intelligence system that resizes proteins and peptides that survived concentrated sulphuric acid each test a different link in it, from how DNA is copied to what a folded protein can withstand.
UPSC has asked
- Prelims 2020: what artificial intelligence can effectively do today
- Prelims 2015: nanotechnology in health, targeted drug delivery and gene therapy
From gene to protein
- A gene is a stretch of deoxyribonucleic acid (DNA) whose sequence of bases spells out one protein.
- The two strands pair adenine with thymine and guanine with cytosine, so each is a template for the other.
- 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.
- Mendel's rules have each of a gene's two copies passed on unchanged and independently, which is the expectation inherited chemical marks break.
How DNA is copied
Unwinding
Helicase spends adenosine triphosphate (ATP) to split the double helix
Fork
A Y shaped replication fork opens where the strands part
Strain
Topoisomerases release the twisting building ahead of the fork
Copying
Each parted strand templates a new partner strand
Why a protein's shape is its function
- The chain folds into helices, sheets and loops, and it is that shape, not the length of the chain, that does the work.
- Peptide bonds break by hydrolysis, which is why a strong acid normally destroys a protein.
What has happened
4 Sep 2026
Certain peptides stayed stable for weeks in 98 per cent sulphuric acid, a first for a biological macromolecule.
- Concentrated sulphuric acid holds almost no water, so little is there to hydrolyse the bonds.
- Nuclear magnetic resonance spectroscopy showed them folding into an omega loop, not helices or sheets.
- Venus's clouds of the acid may then not be too harsh for complex chemistry.
The Hindu, 7 Sep 2026: Sulphuric acid: not so deadly (opens in a new tab)
19 Aug 2026
A study of the replication machinery found a molecular safety catch that keeps the copying apparatus inactive until a chemical signal releases it.
The Hindu, 19 Aug 2026: Helicase, the enzyme that unzips DNA (opens in a new tab)
10 Aug 2026
DNA methylation mapped by nanopore sequencing across two mouse strains showed more than 500 instances of inheritance Mendel's rules do not predict.
- 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.
9 Aug 2026
Raygun, an artificial intelligence system built on protein language models, resizes or rewrites a protein at a chosen length while keeping it working.
- Six of eight shrunken fluorescent proteins still glowed, surviving more than forty coordinated edits where four or five uncoordinated ones killed fluorescence.
- They glow only dimly, so the method needs refinement.
- Gene therapy is the use in view: viral shells carrying genes into cells have a size limit many genes exceed.