In genetics and bioinformatics, a single-nucleotide polymorphism is a germline substitution of a single nucleotide at a specific position in the genome that is present in a sufficiently large fraction of the population.
The International HapMap Project was an organization that aimed to develop a haplotype map (HapMap) of the human genome, to describe the common patterns of human genetic variation. HapMap is used to find genetic variants affecting health, disease and responses to drugs and environmental factors. The information produced by the project is made freely available for research.
A DNA segment is identical by state (IBS) in two or more individuals if they have identical nucleotide sequences in this segment. An IBS segment is identical by descent (IBD) in two or more individuals if they have inherited it from a common ancestor without recombination, that is, the segment has the same ancestral origin in these individuals. DNA segments that are IBD are IBS per definition, but segments that are not IBD can still be IBS due to the same mutations in different individuals or recombinations that do not alter the segment.
Human genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population (alleles), a situation called polymorphism.
Haploview is a commonly used bioinformatics software which is designed to analyze and visualize patterns of linkage disequilibrium (LD) in genetic data. Haploview can also perform association studies, choosing tagSNPs and estimating haplotype frequencies. Haploview is developed and maintained by Dr. Mark Daly's lab at the MIT/Harvard Broad Institute.
The common disease-common variant hypothesis predicts that common disease-causing alleles, or variants, will be found in all human populations which manifest a given disease. Common variants are known to exist in coding and regulatory sequences of genes. According to the CD-CV hypothesis, some of those variants lead to susceptibility to complex polygenic diseases. Each variant at each gene influencing a complex disease will have a small additive or multiplicative effect on the disease phenotype. These diseases, or traits, are evolutionarily neutral in part because so many genes influence the traits. The hypothesis has held in the case of putative causal variants in apolipoprotein E, including APOE ε4, associated with Alzheimer's disease. IL23R has been found to be associated with Crohn's disease; the at-risk allele has a frequency 93% in the general population.
Zinc transporter 8 (ZNT8) is a protein that in humans is encoded by the SLC30A8 gene. ZNT8 is a zinc transporter related to insulin secretion in humans. In particular, ZNT8 is critical for the accumulation of zinc into beta cell secretory granules and the maintenance of stored insulin as tightly-packaged hexamers. Certain alleles of the SLC30A8 gene may increase the risk for developing type 2 diabetes, but a loss-of-function mutation appears to greatly reduce the risk of diabetes.
In genomics, a genome-wide association study, is an observational study of a genome-wide set of genetic variants in different individuals to see if any variant is associated with a trait. GWA studies typically focus on associations between single-nucleotide polymorphisms (SNPs) and traits like major human diseases, but can equally be applied to any other genetic variants and any other organisms.
The Single Nucleotide Polymorphism Database (dbSNP) is a free public archive for genetic variation within and across different species developed and hosted by the National Center for Biotechnology Information (NCBI) in collaboration with the National Human Genome Research Institute (NHGRI). Although the name of the database implies a collection of one class of polymorphisms only, it in fact contains a range of molecular variation: (1) SNPs, (2) short deletion and insertion polymorphisms (indels/DIPs), (3) microsatellite markers or short tandem repeats (STRs), (4) multinucleotide polymorphisms (MNPs), (5) heterozygous sequences, and (6) named variants. The dbSNP accepts apparently neutral polymorphisms, polymorphisms corresponding to known phenotypes, and regions of no variation. It was created in September 1998 to supplement GenBank, NCBI’s collection of publicly available nucleic acid and protein sequences.
Christopher Paul Ponting is a British computational biologist, specializing in the evolution and function of genes and genomes. He is currently Chair of Medical Bioinformatics at the University of Edinburgh and group leader in the MRC Human Genetics Unit. He is also an Associate Faculty member of the Wellcome Trust Sanger Institute, a Fellow of the Academy of Medical Sciences, member of the European Molecular Biology Organisation and Fellow of the Royal Society of Edinburgh. His research focuses on long noncoding RNA function and evolution, on single cell biology and on disease genomics. Outside of science, Chris is an amateur novelist and wrote an unpublished, science fiction novel about engineered viruses.
A reference genome is a digital nucleic acid sequence database, assembled by scientists as a representative example of the set of genes in one idealized individual organism of a species. As they are assembled from the sequencing of DNA from a number of individual donors, reference genomes do not accurately represent the set of genes of any single individual organism. Instead a reference provides a haploid mosaic of different DNA sequences from each donor. For example, the most recent human reference genome is derived from >60 genomic clone libraries. There are reference genomes for multiple species of viruses, bacteria, fungus, plants, and animals. Reference genomes are typically used as a guide on which new genomes are built, enabling them to be assembled much more quickly and cheaply than the initial Human Genome Project. Reference genomes can be accessed online at several locations, using dedicated browsers such as Ensembl or UCSC Genome Browser.
Genomic structural variation is the variation in structure of an organism's chromosome. It consists of many kinds of variation in the genome of one species, and usually includes microscopic and submicroscopic types, such as deletions, duplications, copy-number variants, insertions, inversions and translocations. Originally, a structure variation affects a sequence length about 1kb to 3Mb, which is larger than SNPs and smaller than chromosome abnormality. However, the operational range of structural variants has widened to include events > 50bp. The definition of structural variation does not imply anything about frequency or phenotypical effects. Many structural variants are associated with genetic diseases, however many are not. Recent research about SVs indicates that SVs are more difficult to detect than SNPs. Approximately 13% of the human genome is defined as structurally variant in the normal population, and there are at least 240 genes that exist as homozygous deletion polymorphisms in human populations, suggesting these genes are dispensable in humans. Rapidly accumulating evidence indicates that structural variations can comprise millions of nucleotides of heterogeneity within every genome, and are likely to make an important contribution to human diversity and disease susceptibility.
PR domain zinc finger protein 9 is a protein that in humans is encoded by the PRDM9 gene. PRDM9 is responsible for positioning recombination hotspots during meiosis by binding a DNA sequence motif encoded in its zinc finger domain. PRDM9 is the only speciation gene found so far in mammals, and is one of the fastest evolving genes in the genome.
Imputation in genetics refers to the statistical inference of unobserved genotypes. It is achieved by using known haplotypes in a population, for instance from the HapMap or the 1000 Genomes Project in humans, thereby allowing to test for association between a trait of interest and experimentally untyped genetic variants, but whose genotypes have been statistically inferred ("imputed"). Genotype imputation is usually performed on SNPs, the most common kind of genetic variation.
Structural variation in the human genome is operationally defined as genomic alterations, varying between individuals, that involve DNA segments larger than 1 kilo base (kb), and could be either microscopic or submicroscopic. This definition distinguishes them from smaller variants that are less than 1 kb in size such as short deletions, insertions, and single nucleotide variants.
Mark Joseph Daly is Director of the Finnish Institute for Molecular Medicine (FIMM) at the University of Helsinki, a Professor of Genetics at Harvard Medical School, Chief of the Analytic and Translational Genetic Unit at Massachusetts General Hospital, and a member of the Broad Institute of MIT and Harvard. In the early days of the Human Genome Project, Daly helped develop the genetic model by which linkage disequilibrium could be used to map the haplotype structure of the human genome. In addition, he developed statistical methods to find associations between genes and disorders such as Crohn's disease, inflammatory bowel disease, autism and schizophrenia.
Haplogroup E-M2, also known as E1b1a1-M2, is a human Y-chromosome DNA haplogroup. E-M2 is primarily distributed within sub-Saharan Africa. More specifically, E-M2 is the predominant subclade in West Africa, Central Africa, Southern Africa, and the region of the African Great Lakes; it also occurs at moderate frequencies in North Africa and Middle East. E-M2 has several subclades, but many of these subhaplogroups are included in either E-L485 or E-U175. E-M2 is especially common among indigenous Africans who speak Niger-Congo languages, and was spread to Southern Africa and East Africa through the Bantu expansion.
In genetics, a haplotype block is a region of an organism's genome in which there is little evidence of a history of genetic recombination, and which contain only a small number of distinct haplotypes. According to the haplotype-block model, such blocks should show high levels of linkage disequilibrium and be separated from one another by numerous recombination events. The boundaries of haplotype blocks cannot be directly observed; they must instead be inferred indirectly through the use of algorithms. However, some evidence suggests that different algorithms for identifying haplotype blocks give very different results when used on the same data, though another study suggests that their results are generally consistent. The National Institutes of Health funded the HapMap project to catalog haplotype blocks throughout the human genome.
Stacey B. Gabriel is an American geneticist and Senior Director of the Genomics Platform at the Broad Institute. With Eric Lander, she is also the co-director of the National Human Genome Research Institute's sequencing center at the Broad Institute. She was named the "hottest researcher" on Thomson Reuters' list of the World's Most Influential Scientific Minds in 2014. She was given this honor because she published twenty-three of the most cited papers of 2013, more than any other single researcher recorded by Thomson Reuters. She topped the same list again in 2015. She is also an ISI Highly Cited Researcher.
Emmanouil Theophilos Dermitzakis is a Greek human geneticist and professor in the Department of Genetic Medicine and Development at the University of Geneva, where he is also Director of the Health 2030 Genome Center. He is an ISI Highly Cited Researcher and an elected member of the European Molecular Biology Organization. He is a member of the Swiss Institute of Bioinformatics, where his research group is focused on the genetics and genomics of complex traits in humans. He has joined GlaxoSmithKline as Vice President, Computational Biology in R&D.
