Genomes

A genome is the complete set of genetic material present in an organism, cell, or virus. It includes genes, regulatory sequences, and the noncoding regions that influence how genes are expressed. In cellular life, genomes are primarily built from DNA; in many RNA viruses, the genome is made of RNA. The genome provides the blueprint for development, growth, and function, and its organization varies across life forms.

In cellular organisms the genome is organized into chromosomes. Prokaryotes typically have a single circular chromosome, while eukaryotes carry multiple linear chromosomes within a nucleus and may contain additional DNA in mitochondria or chloroplasts. Genome size and content vary greatly: compact bacterial genomes are mostly coding with little noncoding DNA, whereas many eukaryotic genomes contain large amounts of repetitive and regulatory sequences. Mitochondrial and chloroplast genomes are smaller and usually circular, separate from the nuclear genome. Viruses possess a wide range of genome structures, including linear, circular, segmented, and single- or double-stranded configurations.

Genomics is the study of genomes through sequencing and analysis. Modern sequencing technologies—ranging from Sanger sequencing to high-throughput next-generation sequencing and long-read platforms—enable rapid reconstruction of genome sequences. Genome assembly and annotation identify the order of bases and locate genes, regulatory elements, and other features. Comparative genomics explores similarities and differences between species to infer function and evolutionary history.

Applications of genome science span medicine, agriculture, and ecology. In medicine, genomic information supports diagnosis, risk assessment, and personalized therapies. In agriculture, it guides crop improvement and disease resistance. Ethical, legal, and social considerations address privacy, data sharing, and the responsible use of genomic information in society.