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In addition to maintaining the GenBank® nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides analysis and retrieval resources for the data in GenBank and other biological data made available through the NCBI Website. NCBI resources include Entrez, the Entrez Programming Utilities, MyNCBI, PubMed, PubMed Central (PMC), Gene, the NCBI Taxonomy Browser, BLAST, BLAST Link (BLink), Primer-BLAST, COBALT, Splign, RefSeq, UniGene, HomoloGene, ProtEST, dbMHC, dbSNP, dbVar, Epigenomics, Genome and related tools, the Map Viewer, Model Maker, Evidence Viewer, Trace Archive, Sequence Read Archive, BioProject, BioSample, Retroviral Genotyping Tools, HIV-1/Human Protein Interaction Database, Gene Expression Omnibus (GEO), Probe, Online Mendelian Inheritance in Animals (OMIA), the Molecular Modeling Database (MMDB), the Conserved Domain Database (CDD), the Conserved Domain Architecture Retrieval Tool (CDART), Biosystems, Protein Clusters and the PubChem suite of small molecule databases. Augmenting many of the Web applications are custom implementations of the BLAST program optimized to search specialized data sets. All of these resources can be accessed through the NCBI home page at www.ncbi.nlm.nih.gov.

In addition to maintaining the GenBank(R) nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides analysis and retrieval resources for the data in GenBank and other biological data available through NCBI's web site. NCBI resources include Entrez, the Entrez Programming Utilities, My NCBI, PubMed, PubMed Central, Entrez Gene, the NCBI Taxonomy Browser, BLAST, BLAST Link, Electronic PCR, OrfFinder, Spidey, Splign, RefSeq, UniGene, HomoloGene, ProtEST, dbMHC, dbSNP, Cancer Chromosomes, Entrez Genome, Genome Project and related tools, the Trace, Assembly, and Short Read Archives, the Map Viewer, Model Maker, Evidence Viewer, Clusters of Orthologous Groups, Influenza Viral Resources, HIV-1/Human Protein Interaction Database, Gene Expression Omnibus, Entrez Probe, GENSAT, Database of Genotype and Phenotype, Online Mendelian Inheritance in Man, Online Mendelian Inheritance in Animals, the Molecular Modeling Database, the Conserved Domain Database, the Conserved Domain Architecture Retrieval Tool and the PubChem suite of small molecule databases. Augmenting the web applications are custom implementations of the BLAST program optimized to search specialized data sets. These resources can be accessed through the NCBI home page at www.ncbi.nlm.nih.gov.

The National Center for Biotechnology Information has created the dbGaP public repository for individual-level phenotype, exposure, genotype and sequence data and the associations between them. dbGaP assigns stable, unique identifiers to studies and subsets of information from those studies, including documents, individual phenotypic variables, tables of trait data, sets of genotype data, computed phenotype-genotype associations, and groups of study subjects who have given similar consents for use of their data.

We present the completed dataset and clone repository of the Cancer Chromosome Aberration Project (CCAP), an initiative developed and funded through the intramural program of the U.S. National Cancer Institute, to provide seamless linkage of human cytogenetic markers with the primary nucleotide sequence of the human genome. Spaced at 1-2 Mb intervals across the human genome, 1,339 bacterial artificial chromosome (BAC) clones have been localized to chromosomal bands through high-resolution fluorescence in situ hybridization (FISH) mapping. Of these clones, 99.8% can be positioned on the primary human genome sequence and 95% are placed at or close to their precise nucleotide starts and stops. This dataset can be studied and manipulated within generally available public Web sites. The clones are available from a commercial repository. The CCAP BAC clone set provides anchors for the interrogation of gene and sequence involvement in oncogenic and developmental disorders when the starting point is the recognition of a structural, numerical, or interstitial chromosomal aberration. This dataset also provides a current view of the quality and coherence of the available genome sequence and insight into the nucleotide and three-dimensional structures that manifest as Giemsa light and dark chromosomal banding patterns.

In addition to maintaining the GenBank nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides analysis and retrieval resources for the data in GenBank and other biological data made available through NCBI's Web site. NCBI resources include Entrez, the Entrez Programming Utilities, MyNCBI, PubMed, PubMed Central, Entrez Gene, the NCBI Taxonomy Browser, BLAST, BLAST Link (BLink), Electronic PCR, OrfFinder, Spidey, Splign, RefSeq, UniGene, HomoloGene, ProtEST, dbMHC, dbSNP, Cancer Chromosomes, Entrez Genomes and related tools, the Map Viewer, Model Maker, Evidence Viewer, Clusters of Orthologous Groups, Retroviral Genotyping Tools, HIV-1, Human Protein Interaction Database, SAGEmap, Gene Expression Omnibus, Entrez Probe, GENSAT, Online Mendelian Inheritance in Man, Online Mendelian Inheritance in Animals, the Molecular Modeling Database, the Conserved Domain Database, the Conserved Domain Architecture Retrieval Tool and the PubChem suite of small molecule databases. Augmenting many of the Web applications are custom implementations of the BLAST program optimized to search specialized datasets. All of the resources can be accessed through the NCBI home page at: http://www.ncbi.nlm.nih.gov.

To catalog data on chromosomal aberrations in cancer derived from emerging molecular cytogenetic techniques and to integrate these data with genome maps, we have established two resources, the NCI and NCBI SKY/M-FISH & CGH Database and the Cancer Chromosomes database. The goal of the former is to allow investigators to submit and analyze clinical and research cytogenetic data. It contains a karyotype parser tool, which automatically converts the ISCN short-form karyotype into an internal representation displayed in detailed form and as a colored ideogram with band overlay, and also has a tool to compare CGH profiles from multiple cases. The Cancer Chromosomes database integrates the SKY/M-FISH & CGH Database with the Mitelman Database of Chromosome Aberrations in Cancer and the Recurrent Chromosome Aberrations in Cancer database. These three datasets can now be searched seamlessly by use of the Entrez search and retrieval system for chromosome aberrations, clinical data, and reference citations. Common diagnoses, anatomic sites, chromosome breakpoints, junctions, numerical and structural abnormalities, and bands gained and lost among selected cases can be compared by use of the "similarity" report. Because the model used for CGH data is a subset of the karyotype data, it is now possible to examine the similarities between CGH results and karyotypes directly. All chromosomal bands are directly linked to the Entrez Map Viewer database, providing integration of cytogenetic data with the sequence assembly. These resources, developed as a part of the Cancer Chromosome Aberration Project (CCAP) initiative, aid the search for new cancer-associated genes and foster insights into the causes and consequences of genetic alterations in cancer., ((c) 2005 Wiley-Liss, Inc.)

In addition to maintaining the GenBank nucleic acid sequence database, the National Center for Biotechnology Information (NCBI) provides data retrieval systems and computational resources for the analysis of data in GenBank and other biological data made available through NCBI's website. NCBI resources include Entrez, Entrez Programming Utilities, PubMed, PubMed Central, Entrez Gene, the NCBI Taxonomy Browser, BLAST, BLAST Link (BLink), Electronic PCR, OrfFinder, Spidey, RefSeq, UniGene, HomoloGene, ProtEST, dbMHC, dbSNP, Cancer Chromosomes, Entrez Genomes and related tools, the Map Viewer, Model Maker, Evidence Viewer, Clusters of Orthologous Groups (COGs), Retroviral Genotyping Tools, HIV-1/Human Protein Interaction Database, SAGEmap, Gene Expression Omnibus (GEO), Online Mendelian Inheritance in Man (OMIM), the Molecular Modeling Database (MMDB), the Conserved Domain Database (CDD) and the Conserved Domain Architecture Retrieval Tool (CDART). Augmenting many of the Web applications are custom implementations of the BLAST program optimized to search specialized datasets. All of the resources can be accessed through the NCBI home page at http://www.ncbi.nlm.nih.gov.

We have placed 7,600 cytogenetically defined landmarks on the draft sequence of the human genome to help with the characterization of genes altered by gross chromosomal aberrations that cause human disease. The landmarks are large-insert clones mapped to chromosome bands by fluorescence in situ hybridization. Each clone contains a sequence tag that is positioned on the genomic sequence. This genome-wide set of sequence-anchored clones allows structural and functional analyses of the genome. This resource represents the first comprehensive integration of cytogenetic, radiation hybrid, linkage and sequence maps of the human genome; provides an independent validation of the sequence map and framework for contig order and orientation; surveys the genome for large-scale duplications, which are likely to require special attention during sequence assembly; and allows a stringent assessment of sequence differences between the dark and light bands of chromosomes. It also provides insight into large-scale chromatin structure and the evolution of chromosomes and gene families and will accelerate our understanding of the molecular bases of human disease and cancer.

While high quality information regarding variation in genes is currently available in locus-specific or specialized mutation databases, the need remains for a general catalog of genome variation to address the large-scale sampling designs required by association studies, gene mapping, and evolutionary biology. In response to this need, the National Center for Biotechnology Information (NCBI) has established the dbSNP database http://ncbi. nlm.nih.gov/SNP/ to serve as a generalized, central variation database. Submissions to dbSNP will be integrated with other sources of information at NCBI such as GenBank, PubMed, LocusLink, and the Human Genome Project data, and the complete contents of dbSNP are available to the public via anonymous FTP. Hum Mutat 15:68-75, 2000. Published 2000 Wiley-Liss, Inc.

Our previous work applied neural network techniques to the problem of discriminating open reading frame (ORF) sequences taken from introns versus exons. The method counted the codon frequencies in an ORF of a specified length, and then used this codon frequency representation of DNA fragments to train a neural net (essentially a Perceptron with a sigmoidal, or "soft step function", output) to perform this discrimination. After training, the network was then applied to a disjoint "predict" set of data to assess accuracy. The resulting accuracy in our previous work was 98.4%, exceeding accuracies reported in the literature at that time for other algorithms. Here, we report even higher accuracies stemming from calculations of mutual information (a correlation measure) of spatially separated codons in exons, and in introns. Significant mutual information exists in exons, but not in introns, between adjacent codons. This suggests that dicodon frequencies of adjacent codons are important for intron/exon discrimination. We report that accuracies obtained using a neural net trained on the frequency of dicodons is significantly higher at smaller fragment lengths than even our original results using codon frequencies, which were already higher than simple statistical methods that also used codon frequencies. We also report accuracies obtained from including codon and dicodon statistics in all six reading frames, i.e. the three frames on the original and complement strand. Inclusion of six-frame statistics increases the accuracy still further. We also compare these neural net results to a Bayesian statistical prediction method that assumes independent codon frequencies in each position. The performance of the Bayesian scheme is poorer than any of the neural based schemes, however many methods reported in the literature either explicitly, or implicitly, use this method. Specifically, Bayesian prediction schemes based on codon frequencies achieve 90.9% accuracy on 90 codon ORFs, while our best neural net scheme reaches 99.4% accuracy on 60 codon ORFs. "Accuracy" is defined as the average of the exon and intron sensitivities. Achievement of sufficiently high accuracies on short fragment lengths can be useful in providing a computational means of finding coding regions in unannotated DNA sequences such as those arising from the mega-base sequencing efforts of the Human Genome Project. We caution that the high accuracies reported here do not represent a complete solution to the problem of identifying exons in "raw" base sequences. The accuracies are considerably lower from exons of small length, although still higher than accuracies reported in the literature for other methods. Short exon lengths are not uncommon.(ABSTRACT TRUNCATED AT 400 WORDS)

We present a method for determining preference for methylation at minor methylation sites. The target DNA sequence is first subjected to computer-assisted analysis to predict which restriction endonuclease(s) will generate fragments that will contain only one or two likely minor methylation site(s). The target DNA is then methylated in vitro with a radioactive methyl-group donor and subjected to digestion by the chosen restriction enzyme(s). The amount of radioactivity in the various fragments is determined, after separating them using polyacrylamide gel electrophoresis. We documented the effect of nearby bases on the methylation preference and the relative preference for methylation at some specific minor methylation sites.

A FORTRAN program for displaying the correspondence between codon changes and different possible base changes is presented. Changes of both single bases and dimers are considered. The user can specify the mutagenesis spectrum. Additionally, the user can choose whether or not to consider single or double events in a codon and whether or not to consider the possibility that the change of two bases (a dimer) can overlap a codon boundary. Furthermore, a variety of ways may be chosen to display and summarize the codon changes that can result from the specified mutagenesis. A user-supplied sequence or the genetic code table can be analyzed.

This work is an investigation of the practicality of kinetic control of the length of very short deoxynucleotide homopolymeric additions by terminal deoxynucleotidyltransferase. For such very short additions, the possibility that terminal deoxynucleotidyltransferase acts differently with each deoxytriphosphate, or shows interaction effects when presented with multiple deoxytriphosphates, was investigated. Different relative rates of priming and different relative rates of subsequent additions were found for each deoxytriphosphate. Each triphosphate reacted uniquely, and one case of interaction was found, with adenosine interfering with cytidine addition.

A technique to quantitate small volumes of dilute solutions of different-sized DNA fragments has been developed. The detection limit was 0.7 micrograms/ml and the technique could be used even in the presence of diffusable substances, including those such as sodium dodecyl sulfate which affect surface tension and also exhibit fluorescence when stained with ethidium bromide and excited by ultraviolet light. The DNA was mixed with low-melting-point agarose and pipetted into preformed wells in an agarose plate, where it solidified. After diffusion of small molecules, the amount of DNA was estimated by comparing ethidium bromide-mediated fluorescence of samples with that of standards.

T4 bacteriophage mutants selected for their ability to grow with cytosine in their DNA are defective in host transcriptional shutoff and host chromosome unfolding. The host RNA polymerase purifed from cells infected by such a mutant lacks a small T4-coded subunit.

The limitations of current mutagenesis techniques are analyzed in terms of the number and kinds of codon changes they make and in terms of the population size needed to produce all single or multiple amino acid variants. It is shown how a technique that can alter a single codon of a gene, producing all possible variant codons without affecting the rest of the gene, has certain advantages, if it can be used at each place in the gene in one experiment. Such a technique has advantages when the goals are to understand: (1) how specific structural alterations in a mutant protein cause it to function in a different but specific way, (2) how to predict which amino acids in a protein contact or interact with each other, and (3) why a protein is more or less sensitive to mutational disruption, depending upon the specific mutation. This is because it would generate the maximum number of (1) mutant proteins with different functions, (2) intracistronic suppressor for any starting mutation, and (3) random amino acid substitutions at random places. Furthermore, such a technique could produce useful variants more quickly and on a smaller scale than either evolution or current methods.

We have continued the transcriptional analysis of the region of cytological locus 67B that contains the four small heat shock genes and other genes. Transcription from one of the heat shock genes in the region, hsp 26, takes place during high temperature treatment and at certain developmental stages, without heat shock, in several tissues, such as imaginal discs and adult ovaries. Observations of unexpected products after nuclease protection experiments provided the first indication of what genomic blot experiments showed to be small deletions. The alleles containing the deletion are expressed at the same level as the wild type allele. The deletion shortens the protein product, implying that it is in the coding region. Furthermore, flies homozygous for one of the deletion alleles are viable.

The distribution of interspersed repetitive DNA sequences in the human genome has been investigated, using a combination of biochemical, cytological, computational, and recombinant DNA approaches. "Low-resolution" biochemical experiments indicate that the general distribution of repetitive sequences in human DNA can be adequately described by models that assume a random spacing, with an average distance of 3 kb. A detailed "high-resolution" map of the repetitive sequence organization along 400 kb of cloned human DNA, including 150 kb of DNA fragments isolated for this study, is consistent with this general distribution pattern. However, a higher frequency of spacing distances greater than 9.5 kb was observed in this genomic DNA sample. While the overall repetitive sequence distribution is best described by models that assume a random distribution, an analysis of the distribution of Alu repetitive sequences appearing in the GenBank sequence database indicates that there are local domains with varying Alu placement densities. In situ hybridization to human metaphase chromosomes indicates that local density domains for Alu placement can be observed cytologically. Centric heterochromatin regions, in particular, are at least 50-fold underrepresented in Alu sequences. The observed distribution for repetitive sequences in human DNA is the expected result for sequences that transpose throughout the genome, with local regions of "preference" or "exclusion" for integration.