Scientist found Anolis to have the most compositionally homogeneous genome of all amniotes sequenced thus far, a homogeneity exceeding that for the frog Xenopus. Isochores are large regions of relatively homogeneous nucleotide composition and are present in the genomes of all mammals and birds that have been sequenced to date. GC-rich isochores, with shorter introns and higher gene density are reported in all genomes sequenced till date, but disappeared from the Anolis genome. Using genic GC as a proxy for isochore structure so as to compare with other vertebrates, researchers found that GC content has substantially decreased in the lineage leading to Anolis since diverging from the common ancestor of Reptilia ∼275 MYA, perhaps reflecting weakened or reversed GC-biased gene conversion, a non-adaptive substitution process that is thought to be important in the maintenance and trajectory of isochore evolution.
Results demonstrate that GC composition in Anolis is not associated with important features of genome structure, including gene density and intron size, in contrast to patterns seen in mammal and bird genomes.
Findings are published in the latest issue of Genome Biology and Evolution
No comments:
Post a Comment