Physical activity to improve cognition in older adults: can physical activity programs enriched with cognitive challenges enhance the effects? A systematic review and meta-analysis

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Linked read technology for assembling large complex and polyploid genomes

Background: Short read DNA sequencing technologies have revolutionized genome assembly by providing high accuracy and throughput data at low cost. But it remains challenging to assemble short read data, particularly for large, complex and polyploid genomes. The linked read strategy has the potential to enhance the value of short reads for genome assembly because all reads originating from a single long molecule of DNA share a common barcode. However, the majority of studies to date that have employed linked reads were focused on human haplotype phasing and genome assembly. Results: Here we describe a de novo maize B73 genome assembly generated via linked read technology which contains ~ 172,000 scaffolds with an N50 of 89 kb that cover 50% of the genome. Based on comparisons to the B73 reference genome, 91% of linked read contigs are accurately assembled. Because it was possible to identify errors with \u3e 76% accuracy using machine learning, it may be possible to identify and potentially correct systematic errors. Complex polyploids represent one of the last grand challenges in genome assembly. Linked read technology was able to successfully resolve the two subgenomes of the recent allopolyploid, proso millet (Panicum miliaceum). Our assembly covers ~ 83% of the 1 Gb genome and consists of 30,819 scaffolds with an N50 of 912 kb. Conclusions: Our analysis provides a framework for future de novo genome assemblies using linked reads, and we suggest computational strategies that if implemented have the potential to further improve linked read assemblies, particularly for repetitive genomes

Subunit Structure and Conformations of Tubulin Protofilaments

Microtubules are structural elements of eukaryotic cells which are important for cell motility, cell shape, and cytoplasmic transport (for a review see Kirschner, 1978). One of their characteristic features is the rapid assembly when the cell needs them for a specific purpose such as mitosis, and their disappearance after use. To understand their function one would therefore like to know not only the structure of microtubules but also that of microtubule precursors which might shed light on the process of assembly. The overall shape of flagellar microtubules has been studies by X-ray diffraction, electron microscopy and image proeessing techniques (Grimstone and Klug, 1966; Cohen et al., 1971; Tilney et al., 1973; Arnos and Klug, 1974; and others). They are hollow cylinders of 11 nm mean radius, consisting of 13 protofilaments parallel to the tubule axis. The protofilaments are made up of tubulin monomers of molecular weight 55,000, paired into heterodimers of alpha and beta tubulin. The axial repeat of monomers is 4 nm, their stagger in adjacent protofilaments is about 1 nm