A genome is a hierarchy of scale: chromosomes contain genes, genes are made of exons/introns, and every base of every gene is one of four nucleotides (A, T, G, C) paired across the double helix by hydrogen bonds — A–T (2 bonds) and G–C (3 bonds).
Helix pitch: ~10.5 bp / turn, 0.34 nm rise per bp
GC pairs (3 H-bonds) are thermally more stable than AT pairs (2 H-bonds)
SNP: a single base substituted relative to the reference sequence
- Base pairs shown — length of the helix segment rendered.
- GC content — fraction of G–C pairs (yellow rungs) vs A–T pairs (cyan rungs); real genomes range ~25–75% depending on organism.
- Mutation rate — fraction of bases randomly flagged as single-nucleotide variants (red), the raw material genome-wide association studies (GWAS) scan for.
- Zoom preset — genome (compact, whole-chromosome framing), gene (a highlighted transcribed locus), base-pair (close on individual rungs).
Real-world relevance: whole-genome sequencing reads millions of these base pairs to find the SNPs and structural variants linked to disease risk and personalised medicine.