Every organism carries a complete set of genetic instructions. The genome is the entirety of an organism’s DNA, including all genes and non-coding sequences. In humans the genome comprises approximately 3.2 billion base pairs distributed across 23 chromosome pairs plus mitochondrial DNA.

Genome size and gene number vary widely among species. Sequencing a genome reveals its content, organization, and variation. Reference genomes provide a framework for comparing individuals and studying evolution. Most of the human genome does not code for proteins yet contains essential regulatory elements.

Large-scale projects have sequenced thousands of human genomes and the genomes of many other species. Comparative genomics identifies conserved regions and species-specific innovations. Personal genome sequencing is becoming clinically relevant for rare disease diagnosis and pharmacogenomics.

• Complete set of genetic material in an organism
• Includes genes and non-coding DNA
• Human genome is about 3.2 billion base pairs
• Mapped and studied through sequencing projects