Congenital heart disease (CHD) is one of the commonest human birth defects, with a widely reported birth incidence of just less than 1%, and it accounts for one-third of infant deaths that result from congenital malformation. Epidemiological studies have long suggested that genetic factors may have a contribution to cardiac maldevelopment in humans. Mapping genes by linkage seeks to identify which DNA sequences have been inherited in common by affected individuals in families with multiple members suffering from the genetic disease. Many disease genes have also been identified by studying individuals with a chromosomal rearrangement, such as a translocation, where a piece of chromosomal material breaks of and rejoins to another chromosome. The first draft of human genome sequence was published in 2001 and in 2003 the International Human Genome Sequencing Consortium announced a finished version which detailed the entire DNA sequence of each chromosome.