Many sequence variants affecting diversity of adult human height

Adult human height is one of the classical complex human traits. We searched for sequence variants that affect height by scanning the genomes of 25,174 Icelanders, 2,876 Dutch, 1,770 European Americans and 1,148 African Americans. We then combined these results with previously published results from the Diabetes Genetics Initiative on 3,024 Scandinavians and tested a selected subset of SNPs in 5,517 Danes. We identified 27 regions of the genome with one or more sequence variants showing significant association with height. The estimated effects per allele of these variants ranged between 0.3 and 0.6 cm and, taken together, they explain around 3.7% of the population variation in height. The genes neighboring the identified loci cluster in biological processes related to skeletal development and mitosis. Association to three previously reported loci are replicated in our analyses, and the strongest association was with SNPs in the ZBTB38 gene.     

Enriching Service-Learning by Developing e-Tutoring in Foster Homes

In view of the learning divide between the children in ordinary families and those in foster homes, online one-to-one tutoring has been provided by university students as a service-learning option. Through the synchronous e-tutoring system platform, the goal of this study is to develop a service learning mode for creating campus-community partnerships and mutual learning experiences. Thus the study applies Ramsden’s theory of university teaching (2003) into an action research project for investigating (i) how e-tutoring can solve the problems occurring in face-to-face tutoring in foster homes; (ii) the effects of e-tutoring; (iii) the new issues identified; and (iv) new strategies for future iterations of the program. For explaining a social phenomenon through a theoretical framework, grounded theory analysis was applied and eight themes were identified in the qualitative data of 10 observation reports, 28 interviews, and 140 weekly journals from both ends of two foster homes and one university. Eight subcategories (content and learning, practical learning, tutoring concerns, knowledge gains, competency gains, adult guidance, e-tutoring approaches, and transformative development) are categorized along with Ramsden’s hierarchy theory—teaching as telling or transmission, teaching as organizing student activity, and teaching as making learning possible. With transformative development of the campus-community partnership the consensus goal among university faculty, directors of foster homes and relevant personnel of e-tutoring (Enos and Morton 2003), the study discussed future improvements for the e-tutoring program. The action research strongly suggests that e-tutoring should emphasize more reflective listening rather than subject-mattered achievement and turn service-learning into an opportunity of achieving the sustainable integration of community resources and social welfare institutions.     

Fine-scale recombination rate differences between sexes, populations and individuals

Meiotic recombinations contribute to genetic diversity by yielding new combinations of alleles. Recently, high-resolution recombination maps were inferred from high-density single-nucleotide polymorphism (SNP) data using linkage disequilibrium (LD) patterns that capture historical recombination events. The use of these maps has been demonstrated by the identification of recombination hotspots and associated motifs, and the discovery that the PRDM9 gene affects the proportion of recombinations occurring at hotspots. However, these maps provide no information about individual or sex differences. Moreover, locus-specific demographic factors like natural selection can bias LD-based estimates of recombination rate. Existing genetic maps based on family data avoid these shortcomings, but their resolution is limited by relatively few meioses and a low density of markers. Here we used genome-wide SNP data from 15,257 parent-offspring pairs to construct the first recombination maps based on directly observed recombinations with a resolution that is effective down to 10 kilobases (kb). Comparing male and female maps reveals that about 15% of hotspots in one sex are specific to that sex. Although male recombinations result in more shuffling of exons within genes, female recombinations generate more new combinations of nearby genes. We discover novel associations between recombination characteristics of individuals and variants in the PRDM9 gene and we identify new recombination hotspots. Comparisons of our maps with two LD-based maps inferred from data of HapMap populations of Utah residents with ancestry from northern and western Europe (CEU) and Yoruba in Ibadan, Nigeria (YRI) reveal population differences previously masked by noise and map differences at regions previously described as targets of natural selection.     

Rate of de novo mutations and the importance of father's age to disease risk

Mutations generate sequence diversity and provide a substrate for selection. The rate of de novo mutations is therefore of major importance to evolution. Here we conduct a study of genome-wide mutation rates by sequencing the entire genomes of 78 Icelandic parent-offspring trios at high coverage. We show that in our samples, with an average father's age of 29.7, the average de novo mutation rate is 1.20?×?10(-8) per nucleotide per generation. Most notably, the diversity in mutation rate of single nucleotide polymorphisms is dominated by the age of the father at conception of the child. The effect is an increase of about two mutations per year. An exponential model estimates paternal mutations doubling every 16.5?years. After accounting for random Poisson variation, father's age is estimated to explain nearly all of the remaining variation in the de novo mutation counts. These observations shed light on the importance of the father's age on the risk of diseases such as schizophrenia and autism.