Combining new and existing genomic data on cheilostome bryozoans — a group of ubiquitous, species-rich, marine colonial organisms — a team led by scientists from the University of Oslo has uncovered new details about the evolutionary origins of the animals. While cheilostome bryozoans have an excellent fossil record extending back hundreds of millions of years, they lack phylogenetic relationships inferred from molecular data. As reported in this week's Science Advances, the researchers combined genome-skimmed molecular data from the mitochondrial genome and two nuclear ribosomal RNA genes for 395 newly sequenced cheilostome specimens with published sequences for 340 other specimens. They then used these data to infer relationships and the timing of key events among roughly 500 cheilostome species. Among their findings is evidence that the cheilostome lineage could have Paleozoic origins, much older than the first known fossil record of cheilostomes in the Late Jurassic.
The complete sequence of a human genome, covering the 8 percent of the genome that had previously been unresolved, is presented in Science this week. Since the human reference genome was first released, it has only covered the euchromatic fraction of the genome, leaving important heterochromatic regions unfinished. To address this, the Telomere-to-Telomere Consortium generated a complete 3.055 billion-base pair sequence of a human genome — called T2T-CHM13 — that includes gapless assemblies for all chromosomes except Y, corrects errors in the prior references, and introduces nearly 200 million base pairs of sequence containing 1,956 gene predictions, many of which are predicted to be protein coding. "The completed regions include all centromeric satellite arrays, recent segmental duplications, and the short arms of all five acrocentric chromosomes, unlocking these complex regions of the genome to variational and functional studies," the consortium members write.