Low-pass single-chromosome sequencing of human small supernumerary marker chromosomes (sSMCs) and Apodemus B chromosomes.

Supernumerary chromosomes sporadically arise in many eukaryotic species as a result of genomic rearrangements. If present in a substantial part of species population, those are called B chromosomes, or Bs. This is the case for 70 mammalian species, most of which are rodents. In humans, the most common types of extra chromosomes, sSMCs (small supernumerary marker chromosomes), are diagnosed in approximately 1 of 2000 postnatal cases. Due to low frequency in population, human sSMCs are not considered B chromosomes. Genetic content of both B-chromosomes and sSMCs in most cases remains understudied. Here, we apply microdissection of single chromosomes with subsequent low-pass sequencing on Ion Torrent PGM and Illumina MiSeq to identify unique and repetitive DNA sequences present in a single human sSMC and several B chromosomes in mice Apodemus flavicollis and Apodemus peninsulae. The pipeline for sequencing data analysis was made available in Galaxy interface as an addition to previously published command-line version. Human sSMC was attributed to the proximal part of chromosome 15 long arm, and breakpoints leading to its formation were located into satellite DNA arrays. Genetic content of Apodemus B chromosomes was species-specific, and minor alterations were observed in both species. Common features of Bs in these Apodemus species were satellite DNA and ERV enrichment, as well as the presence of the vaccinia-related kinase gene Vrk1. Understanding of the non-essential genome elements content provides important insights into genome evolution in general.This is a post-peer-review, pre-copyedit version of an article published in Chromosoma. The final authenticated version is available online at: [http://dx.doi.org/10.1007/s00412-018-0662-0

Radiation Chemistry of Overirradiated Aqueous Solutions of Hydrogen Cyanide and Ammonium Cyanide

The radiolysis of aqueous solutions (O2-free) of HCN and NH4CN was examined at very large doses of 60Co gamma radiation (up to 230 Mrad). In this dose range the cyanide initially present (0.12 M) is decomposed and only its radiolytic products participate in the radiation-induced chemical process. It has been found that the weight of the dry residue containing the mixture of nonvolatile radiolytic products increases as doses increase up to 40 Mrad (up to about 4 g/l), but with further dose increases remains practically unchanged (NH4CN) or decreases slightly (HCN). Carboxylic and amino acids are present in overirradiated samples. At increasing doses their concentrations decrease, with the exception of oxalic and malonic acids, which are continually produced and accumulate. This is also the case with the abundant NH3 and CO2, as well as with several other products that were generated at lower radiation-chemical yields. The molecular weights of the radiolytic products are up to 20,000 daltons throughout the dose range studied. Their amounts gradually change with increasing doses above 30 Mrad: The compounds with Mw between 2,000 and 6,000 daltons become more abundant, while the amounts of polymers with Mw between 6,000 and 20,000 decrease. The relevance of these findings for studies of chemical evolution is considered