Excerpt from exon 1
A journey from the double helix down to a single hydrogen bond — driven entirely by scrolling.
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Zoom level 1 / 5 – Molecular level
DNA consists of two strands wound around each other in opposite directions (antiparallel). The backbone that gives DNA its name — made of sugar (deoxyribose) and phosphate — is chemically identical on both strands; only the bases on the inside differ from position to position.
Zoom level 2 / 5 – Chromosome level
Inside the cell nucleus, DNA doesn't exist as a free-floating strand. It is wound around histone proteins and packaged, in humans, into 46 chromosomes (23 pairs). Each chromosome contains millions of base pairs — and thousands of genes are distributed across it.
Every chromosome has a short arm (p) and a long arm (q), meeting at the centromere. Exons — the coding sections of a gene — are scattered across the entire chromosome, alternating with non-coding introns.
Zoom level 3 / 5 – Genome segments
Viewed linearly, DNA isn't continuously "active." Coding sections (exons) alternate with non-coding introns; regulatory regions such as promoters determine when and how often a gene is read.
By far the largest part of the human genome is non-coding — the actual genes make up only a small fraction.
Zoom level 4 / 5 – Base sequence
Within a coding section, the sequence is read in groups of three — codons. Each codon stands for a specific amino acid or marks the start or stop of translation into a protein.
Zoom level 5 / 5 – Chemical structure
At the molecular level, bases pair according to fixed rules: adenine with thymine via two hydrogen bonds, guanine with cytosine via three. This specificity is the basis for faithfully duplicating DNA at every cell division.