Genome
A genome is the complete set of DNA instructions that define an organism—its blueprint for building proteins, regulating traits, and passing information to offspring. The term comes from "gene" and "chromosome," and it encompasses both protein-coding sequences and vast regions of regulatory or "non-coding" DNA.
Genomes vary wildly in size and complexity. A bacterium's genome might contain 4 million base pairs, while a human genome contains roughly 3 billion. Yet genome size doesn't correlate neatly with organism complexity—some plants have larger genomes than humans, a puzzle called the C-value paradox.
Understanding genomes revolutionized Evolutionary Biology, revealing kinship between all living things and how Natural selection sculpts inherited variation. Today, genome sequencing is routine and cheap, enabling everything from personalized medicine to Agricultural development and tracing Human migration.
The genome is not destiny, though: Gene expression responds to environment and chance. Epigenetics shows how chemical tags switch genes on and off without changing the underlying DNA sequence itself. This dance between genetic code and context defines what it means to be alive.