ABSTRACT
In addition to human genomes, the genome sequencing revolution has also been applied to very many animal genomes, and in this chapter, the authors address aspects of genetic variation between species. The authors cover how comparative genomics was established, and how it depends on powerful computer programs that enable sequence comparisons and alignment at the genome level. The authors describe phylogenetic approaches and give an overview of where humans fit in within the Tree of Life. Here, they primarily concentrate on the evolution of genome size (with the involvement of whole-genome duplication and gene duplication), differences between species in gene number, and the advantages of both gene duplication and exons. Cross-species comparisons have demonstrated increasing protein and gene sequence complexity during the evolution of biologically complex organisms. Gene families are a major general feature of metazoan genomes, and emerged as a result of different gene duplication events in germ-line DNA.
