The science of genetics focuses on genes as the units of heredity, and how that information is transmitted. At an entirely different level, genomics focuses on the entire genome of an organism, which comprises all of its genetic information. The field of genomics is divided into several categories, including functional and comparative genomics. While functional genomics is concerned mainly with how genes and the genome function in a given organism, comparative genomics focuses on comparing genomes from different species.
Comparative genomics is a useful topic of study for many reasons. One is that examining and comparing the genomes of a variety of different species provides information about how evolutionary selection acts on the genome. Although this field is still young, it may be able to shed a great deal of light on aspects of recent events in evolution. Another important facet of this scientific discipline is the study of comparative human genomics.
Scientists who study comparative genomics may examine one or more features of various different genomes. These features may include locations of genes, similarity of sequences of genes, and the distribution of coding and non-coding regions in individual genes and the genome as a whole. By examining the differences between genomes of a variety of species, it is possible to determine the types of genes which are similar or divergent among species. This information can be used to explore how evolution has acted on the genomes of these species.
Within the field of human genomics, there is enormous potential for significant advances in medical research. For example, studying the human genome may provide information about targets for new pharmaceuticals, and even allow for the possibility of individualizing drugs on a case-by-case basis. The development of individualized drug regimens has the potential to significantly reduce the incidence of abnormal drug reactions. These occur because individual variations in the genome cause people to react to medications slightly differently, sometimes in a way which is harmful.
Comparative genomics is useful here because studying simpler organisms such as a mouse or rabbit can provide valuable information about the human genome. This may seem counter-intuitive, but in fact the genomes of these species share many genes in common, making small mammal studies highly relevant to the field of human medicine. The study of comparative human genomics has been furthered by the completion of the Human Genome Project. This project is essentially a map of the entire human genome, which includes somewhere between 20,000 and 25,000 genes. The genomes of many other organisms, including the mouse, have also been mapped.