obsolete haplotype block true Derived from DOI: 10.1126/science.1069424 and http://purl.obolibrary.org/obo/SO_0000355 ! haplotype_block. Decided to represent haplotypes as collections of discrete alleles, rather than continuous features defined by such sets. A sequence feature representing a region of the genome over which there is little evidence for historical recombination, such that sequences it contain are typically co-inherited/transmitted across generations. A haplotype block is a class of genomic sequence defined by a lack of evidence for historical recombination, such that sequence alterations within it tend to be co-inherited across successive generations. A haplotype is considered to be one of many possible versions of a 'haplotype block' - defined by the set of co-inherited alterations it contains. In this sense, the relationship between 'haplotype' and 'haplotype block' is analogous to the relationship between 'gene allele' and 'gene'* - a 'gene allele' is one of many possible instances of a 'gene', while a 'haplotype' is one of many possible instances of a 'haplotype block'. The boundaries of haplotype blocks are defined in efforts to identify haplotypes that exist in organisms or populations. A haplotype block may span any number of sequence alterations, and may cover small or large chromosomal regions - depending on the number of recombination events that have occurred between the alterations defining the haplotype. ----------------------- * One difference however is that gene instnaces are necessarily 'functional' - so non-functional alleles of a gene locus wont qualify as gene instances. no such requirement exists for haplotype block instnaces.