Evidence of Abundant Purifying Selection in Humans for Recently Acquired Regulatory Functions

Abstract

No More Junk DNA The majority of the human genome is transcribed at some level, but the function and evolutionary constraint among regions that do not regulate gene expression or code for genes are generally unknown. Examining data from the 1000 Genomes Project and ENCODE, Ward and Kellis (p. 1675 , published online 5 September) examined regions of the human genome that did not show conservation among mammals and found evidence for a human lineage-specific constraint spanning approximately 4% of the genome that is biochemically active but not directly associated with genes. Interestingly, these regions showed lower numbers of single-nucleotide polymorphisms, heterozygosity, and derived allele frequencies, suggesting that they are under constraint and may be functional.