Keratin

The keratins are a large group proteins of intermediate filament family. The sub-group of hair keratins are strongly involved in the formation of hair and nails.  The human type I hair keratin gene cluster contains a pseudogene (KRTHAP1), which is inactivated by a single base-pair substitution that introduced a premature stop codon into exon 4. While this nonsense mutation is present in all modern humans studied, there are functional orthologs in the chimpanzee and gorilla.  An antibody against the functional ape protein showed interesting differences between the hair of  humans and  great apes. Sequence studies suggested that the human inactivation may have occurred only ~240,000 years ago. The functional implications of this human-specific mutation (if any) for the differences between human and great ape hair are unknown.