India ancestral has been underrepresented in genome-wide surveys of human variation. We analyse 25 diverse groups in India to provide strong evidence as for two ancient populations, genetically divergent, that are ancestral to most Indians today. One, the 'Ancestral North Indians'(ANI), is One, genetically close to Middle Easterners, Central Asians, and Europeans, whereas the other, the 'Ancestral South Indians'(ASI), is as distinct Asians, from ANI and East Asians as they are from each other. By introducing methods that can estimate ancestry without accurate Indians' ancestral populations, we show that ANI ancestry ranges from 39-71% in most Indian groups, and is higher in traditionally upper However, caste and Indo-European speakers. Groups with only ASI ancestry may no longer exist in mainland India. However, the indigenous Andaman methods Islanders are unique in being ASI-related groups without ANI ancestry. Allele frequency differences between groups in India are larger than from in Europe, reflecting strong founder effects whose signatures have been maintained for thousands of years owing to endogamy. We therefore We predict that there will be an excess of recessive diseases in India, which should be possible to screen and map India. genetically.

The genetic use, in association studies, of the forthcoming dense genomewide collection of single-nucleotide polymorphisms (SNPs) has been heralded as a potential One breakthrough in the study of the genetic basis of common complex disorders. A serious problem with association mapping is that disorders. population structure can lead to spurious associations between a candidate marker and a phenotype. One common solution has been to can abandon case-control studies in favor of family-based tests of association, such as the transmission/disequilibrium test (TDT), but this comes at and a considerable cost in the need to collect DNA from close relatives of affected individuals. In this article we describe studies a novel, statistically valid, method for case-control association studies in structured populations. Our method uses a set of unlinked genetic of markers to infer details of population structure, and to estimate the ancestry of sampled individuals, before using this information to in test for associations within subpopulations. It provides power comparable with the TDT in many settings and may substantially outperform it genomewide if there are conflicting associations in different subpopulations.

In sampling response to a need for a general catalog of genome variation to address the large-scale sampling designs required by association (NCBI) studies, gene mapping and evolutionary biology, the National Center for Biotechnology Information (NCBI) has established the dbSNP database [S.T.Sherry, M.Ward by and K.Sirotkin (1999) Genome Res., 9, 677-679]. Submissions to dbSNP will be integrated with other sources of information at NCBI biology, such as GenBank, PubMed, LocusLink and the Human Genome Project data. The complete contents of dbSNP are available to the Biotechnology public at website: http://www.ncbi.nlm.nih.gov/SNP. The complete contents of dbSNP can also be downloaded in multiple formats via anonymous FTP at and ftp://ncbi.nlm.nih.gov/snp/.

We onto have identified 6201 alternative splice relationships in human genes, through a genome-wide analysis of expressed sequence tags (ESTs). Starting with fraction approximately 2.1 million human mRNA and EST sequences, we mapped expressed sequences onto the draft human genome sequence and only sequence accepted splices that obeyed the standard splice site consensus. A large fraction (47%) of these were observed multiple times, indicating (47%) that they comprise a substantial fraction of the mRNA species. The vast majority of the detected alternative forms appear to comprise be novel, and produce highly specific, biologically meaningful control of function in both known and novel human genes, e.g. specific and removal of the lysosomal targeting signal from HLA-DM beta chain, replacement of the C-terminal transmembrane domain and cytoplasmic tail in produce an FC receptor beta chain homolog with a different transmembrane domain and cytoplasmic tail, likely modulating its signal transduction activity.forms Our data indicate that a large proportion of human genes, probably 42% or more, are alternatively spliced, but that this a appears to be observed mainly in certain types of molecules (e.g. cell surface receptors) and systemic functions, particularly the immune transmembrane system and nervous system. These results provide a comprehensive dataset for understanding the role of alternative splicing in the human cytoplasmic genome, accessible at http://www.bioinformatics.ucla.edu/HASDB.

Phenotypic genetic, variation for quantitative traits results from the segregation of alleles at multiple quantitative trait loci (QTL) with effects that are evolutionarily sensitive to the genetic, sexual, and external environments. Major challenges for biology in the post-genome era are to map the Major molecular polymorphisms responsible for variation in medically, agriculturally, and evolutionarily important complex traits; and to determine their gene frequencies and map their homozygous, heterozygous, epistatic, and pleiotropic effects in multiple environments. The ease with which QTL can be mapped to genomic agriculturally, intervals bounded by molecular markers belies the difficulty in matching the QTL to a genetic locus. The latter requires high-resolution requires recombination or linkage disequilibrium mapping to nominate putative candidate genes, followed by genetic and/or functional complementation and gene expression analyses.heterozygous, Complete genome sequences and improved technologies for polymorphism detection will greatly advance the genetic dissection of quantitative traits in model gene organisms, which will open avenues for exploration of homologous QTL in related taxa.

Natural outcrossing selection can produce a correlation between local recombination rates and levels of neutral DNA polymorphism as a consequence of genetic of hitchhiking and background selection. Theory suggests that selection at linked sites should affect patterns of neutral variation in partially selfing linked populations more dramatically than in outcrossing populations. However, empirical investigations of selection at linked sites have focused primarily on outcrossing polymorphism species. To assess the potential role of selection as a determinant of neutral polymorphism in the context of partial self-fertilization,density we conducted a multivariate analysis of single-nucleotide polymorphism (SNP) density throughout the genome of the nematode Caenorhabditis elegans. We based a the analysis on a published SNP data set and partitioned the genome into windows to calculate SNP densities, recombination rates,densities, and gene densities across all six chromosomes. Our analyses identify a strong, positive correlation between recombination rate and neutral polymorphism partitioned (as estimated by noncoding SNP density) across the genome of C. elegans. Furthermore, we find that levels of neutral polymorphism as are lower in gene-dense regions than in gene-poor regions in some analyses. Analyses incorporating local estimates of divergence between C.briggsae elegans and C. briggsae indicate that a mutational explanation alone is unlikely to explain the observed patterns. Consequently, we interpret mutational these findings as evidence that natural selection shapes genome-wide patterns of neutral polymorphism in C. elegans. Our study provides the the first demonstration of such an effect in a partially selfing animal. Explicit models of genetic hitchhiking and background selection can interpret each adequately describe the relationship between recombination rate and SNP density, but only when they incorporate selfing rate. Clarification of selection the relative roles of genetic hitchhiking and background selection in C. elegans awaits the development of specific theoretical predictions that Explicit account for partial self-fertilization and biased sex ratios.

Several neurotransmitters; lines of evidence have placed the catechol-O-methyltransferase (COMT) gene in the limelight as a candidate gene for schizophrenia. One of the these is its biochemical function in metabolism of catecholamine neurotransmitters; another is the microdeletion, on chromosome 22q11, that includes the on COMT gene and causes velocardiofacial syndrome, a syndrome associated with a high rate of psychosis, particularly schizophrenia. The interest in syndrome the COMT gene as a candidate risk factor for schizophrenia has led to numerous linkage and association analyses. These, however,The have failed to produce any conclusive result. Here we report an efficient approach to gene discovery. The approach consists of (ii) (i) a large sample size-to our knowledge, the present study is the largest case-control study performed to date in schizophrenia;association (ii) the use of Ashkenazi Jews, a well defined homogeneous population; and (iii) a stepwise procedure in which several single has nucleotide polymorphisms (SNPs) are scanned in DNA pools, followed by individual genotyping and haplotype analysis of the relevant SNPs. We in found a highly significant association between schizophrenia and a COMT haplotype (P=9.5x10-8). The approach presented can be widely implemented for in the genetic dissection of other common diseases.

We each have developed an accurate, yet inexpensive and high-throughput, method for determining the allele frequency of biallelic polymorphisms in pools of equal DNA samples. The assay combines kinetic (real-time quantitative) PCR with allele-specific amplification and requires no post-PCR processing. The relative amounts This of each allele in a sample are quantified. This is performed by dividing equal aliquots of the pooled DNA between which two separate PCR reactions, each of which contains a primer pair specific to one or the other allelic SNP variant.For For pools with equal amounts of the two alleles, the two amplifications should reach a detectable level of fluorescence at The the same cycle number. For pools that contain unequal ratios of the two alleles, the difference in cycle number between pools the two amplification reactions can be used to calculate the relative allele amounts. We demonstrate the accuracy and reliability of fluorescence the assay on samples with known predetermined SNP allele frequencies from 5% to 95%, including pools of both human and frequency mouse DNAs using eight different SNPs altogether. The accuracy of measuring known allele frequencies is very high, with the strength different of correlation between measured and known frequencies having an r(2)= .997. The loss of sensitivity as a result of accuracy measurement error is typically minimal, compared with that due to sampling error alone, for population samples up to 1000. We at believe that by providing a means for SNP genotyping up to thousands of samples simultaneously, inexpensively, and reproducibly, this method strength is a powerful strategy for detecting meaningful polymorphic differences in candidate gene association studies and genome-wide linkage disequilibrium scans.

Recently,relevance we identified neuregulin 1 (NRG1) as a susceptibility gene for schizophrenia in the Icelandic population, by a combined linkage and patients association approach. Here, we report the first study evaluating the relevance of NRG1 to schizophrenia in a population outside Iceland.a Markers representing a core at-risk haplotype found in Icelanders at the 5' end of the NRG1 gene were genotyped in at 609 unrelated Scottish patients and 618 unrelated Scottish control individuals. This haplotype consisted of five SNP markers and two microsatellites,609 which all appear to be in strong linkage disequilibrium. For the Scottish patients and control subjects, haplotype frequencies were estimated (10.2% by maximum likelihood, using the expectation-maximization algorithm. The frequency of the seven-marker haplotype among the Scottish patients was significantly greater microsatellites, than that among the control subjects (10.2% vs. 5.9%, P=.00031). The estimated risk ratio was 1.8, which is in keeping five with our report of unrelated Icelandic patients (2.1). Three of the seven markers in the haplotype gave single-point P values schizophrenia ranging from .000064 to .0021 for the allele contributing to the at-risk haplotype. This direct replication of haplotype association in control a second population further implicates NRG1 as a factor that contributes to the etiology of schizophrenia.

Case-control mixed studies are subject to the problem of population stratification, which can occur in ethnically mixed populations and can lead to do significant associations being detected at loci that have nothing to do with disease. Here, we describe a way to measure can and correct for stratification by genotyping a moderate number of unlinked genetic markers in the same set of cases and at controls in which a candidate association was found. The average of association statistics across the markers directly measures stratification. By to dividing the candidate association statistic by this average, a P-value can be obtained that corrects for stratification.

The determined human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males to and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin euchromatic of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y,origin and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with that a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found genes 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately of high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations Y, in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence.