ABSTRACT
Genome sequencing cannot at present be accomplished on a single large piece of DNA such as a whole chromosome, so the task is subdivided into smaller parts. New technologies are being developed to sequence longer and longer templates. Shotgun and bacterial artificial chromosome-based methods have been used to sequence larger genomes, as in the Human Genome Project. Lander–Waterman statistics estimate how many sequencing reads will be needed for an entire genome. Assembly of sequence fragments remains a computationally intensive step of the sequencing process. Genes can be located in the genome by extrinsic, ab initio, and comparative approaches. Gene functional annotation helps to determine gene function, and gene ontology facilitates the comparison of genes between organisms. Gene ontologies are a post-annotation tool that can assist in understanding the functional significance of genes in an assembled annotated genome. Next-generation DNA sequencing will continue to get better and cheaper and will expand further the informatics aspect of genomics.
