In this week's Nature Genetics, an international team of researchers reports on a study of the genetic similarities between distantly related marine mammals, providing new insights into how these animals developed similar traits despite their different ancestries. The researchers sequenced the genomes of the killer whale, walrus, and manatee, and refined the genome sequence for the bottlenose dolphin. They identified 191 genes that had been selected for across all four species, suggesting that the genes are related to the shift from terrestrial to marine life, with eight of them undergoing identical molecular changes in all four species. An additional seven genes — some of which are involved in bone formation, inner ear formation, regulation of blood coagulation, and other processes important to marine adaptation — were found to have undergone identical changes in all the species, but only showed evidence of being involved in adaptation in one or two species. GenomeWeb has more on this study here.
Also in Nature Genetics, researchers led by Jiangxi Agricultural University's Lusheng Huang present the results of a whole-genome sequencing study involving 69 pigs from 15 geographically divergent locations in China, offering clues to how the animals have adapted to their local environmental conditions. In a genome-wide scan, they pinpointed a set of loci believed to have a role in regional adaptations to high- and low-latitude environments. They also discovered a region on the X chromosome that appears to have two separate haplotypes in high- and low-latitude populations, possibly underlying their adaptation to cold and hot environments. GenomeWeb has more on this study, too, here.
Finally in Nature Methods, researchers from the Georgia Institute of Technology publish details of a method for systematically profiling ribonucleotide incorporation in genomic DNA. Called ribose-seq, the technique enables the capture of unique products generated by alkaline cleavage of DNA at embedded ribonucleotides. High-throughput sequencing of these fragments in DNA from the yeast Saccharomyces cerevisiae revealed widespread ribonucleotide distribution, with a penchant for cytidine and guanosine, and identified hotspots of ribonucleotide incorporation in nuclear and mitochondrial DNA. Ribonucleotides were found to be primarily incorporated on the newly synthesized leading strand of nuclear DNA and were present upstream of (G+C)-rich tracts in the mitochondrial genome. GenomeWeb also has more on this method here.