Synteny - Shared Synteny

Shared Synteny

Shared synteny (also known as conserved synteny) describes preserved co-localization of genes on chromosomes of different species. During evolution, rearrangements to the genome such as chromosome translocations may separate two loci apart, resulting in the loss of synteny between them. Conversely, translocations can also join two previously separate pieces of chromosomes together, resulting in a gain of synteny between loci. Stronger-than-expected shared synteny can reflect selection for functional relationships between syntenic genes, such as combinations of alleles that are advantageous when inherited together, or shared regulatory mechanisms.

The term is sometimes also used to describe preservation of the precise order of genes on a chromosome passed down from a common ancestor, although many geneticists reject this use of the term. The analysis of synteny in the gene order sense has several applications in genomics. Shared synteny is one of the most reliable criteria for establishing the orthology of genomic regions in different species. Additionally, exceptional conservation of synteny can reflect important functional relationships between genes. For example, the order of genes in the "Hox cluster", which are key determinants of the animal body plan and which interact with each other in critical ways, is essentially preserved throughout the animal kingdom. Patterns of shared synteny or synteny breaks can also be used as characters to infer the phylogenetic relationships among several species, and even to infer the genome organization of extinct ancestral species. A qualitative distinction is sometimes drawn between macrosynteny, preservation of synteny in large portions of a chromosome, and microsynteny, preservation of synteny for only a few genes at a time.