Genetic information storage and processing rely on just two polymers, DNA and RNA. Whether their role reflects evolutionary history or fundamental functional constraints is unknown. Using polymerase evolution and design, we show that genetic information can be stored in and recovered from six alternative genetic polymers (XNAs) based on simple nucleic acid architectures not found in nature. We also select XNA aptamers, which bind their targets with high affinity and specificity, demonstrating that beyond heredity, specific XNAs have the capacity for Darwinian evolution and for folding into defined structures. Thus, heredity and evolution, two hallmarks of life, are not limited to DNA and RNA but are likely to be emergent properties of polymers capable of information storage.The nucleic acids DNA and RNA provide the molecular basis for all life through their unique ability to store and propagate information. To better understand these singular properties and discover relevant parameters for the chemical basis of molecular information encoding, nucleic acid structure has been dissected by systematic variation of nucleobase, sugar and backbone moieties (1-7).These studies have revealed the profound influence of backbone, sugar and base chemistry on nucleic acid properties and function. Crucially, only a small subset of chemistries allows information transfer through base pairing with DNA or RNA, a prerequisite for crosstalk with extant biology. However, base pairing alone cannot conclusively determine the capacity of a given chemistry to serve as a genetic system, as hybridization need not preserve information content (8). A more thorough examination of candidate genetic polymers' potential for information storage, propagation and evolution requires a system for replication which would allow a systematic exploration of the informational, evolutionary and functional potential of synthetic genetic polymers and open up applications ranging from biotechnology to material science.In principle, informational polymers can be synthesized and replicated chemically (9) with advances in the non-enzymatic polymerization of mononucleotides (10) (11, 12) enabling model selection experiments (13). Nevertheless, chemical polymerization remains relatively inefficient. On the other hand, enzymatic polymerization has been hindered by the stringent substrate selectivity of polymerases. Despite progress in understanding the determinants of polymerase substrate specificity and in engineering polymerases with expanded substrate spectra (7), most unnatural nucleotide analogues are poor polymerase substrates at full substitution, both as nucleotides for polymer synthesis and as templates for reverse transcription. Notable exceptions are 2′OMe-DNA and TNA. 2′OMe-DNA is present in eukaryotic rRNAs, is well-tolerated by natural reverse transcriptases (RTs) and has been shown to support heredity and evolution at near full substitution (14). TNA allowed polymer synthesis and evolution in a three letter system (15) but only limited re...

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By using a cre-lox conditional knockout strategy, we report here the generation of androgen receptor knockout (ARKO) mice. Phenotype analysis shows that ARKO male mice have a female-like appearance and body weight. Their testes are 80% smaller and serum testosterone concentrations are lower than in wild-type (wt) mice. Spermatogenesis is arrested at pachytene spermatocytes. The number and size of adipocytes are also different between the wt and ARKO mice. Cancellous bone volumes of ARKO male mice are reduced compared with wt littermates. In addition, we found the average number of pups per litter in homologous and heterozygous ARKO female mice is lower than in wt female mice, suggesting potential defects in female fertility and/or ovulation. The cre-lox ARKO mouse provides a much-needed in vivo animal model to study androgen functions in the selective androgen target tissues in female or male mice

A modified poly(dimethylsiloxane) film with nanopores, fabricated through a scalable and low-cost process, can serve as a protective layer for improving lithium-metal anodes. This film can suppress Li-dendrite formation because of its chemical inertness and mechanical properties. Stable cycling over 200 cycles with an averaged CE of 94.5% is demonstrated at 0.5 mA cm .