KRT31 KRT31 Keratin, type I cuticular Ha1 is a protein that in humans is encoded by the "KRT31" gene. The protein encoded by this gene is a member of the keratin gene family. As a type I hair keratin, it is an acidic protein which heterodimerizes with type II keratins to form hair and nails. The type I hair keratins are clustered in a region of chromosome 17q12-q21 and have the same direction of transcription. Model organisms have been used in the study of KRT31 function. A conditional knockout mouse line called "Krt31" was generated at the Wellcome Trust Sanger Institute.
Human hair color can be found spread around most of Europe. Studies in 2012 showed that naturally blond hair of Melanesians is caused by a recessive mutation in tyrosinase-related protein 1 (TYRP1). In the Solomon Islands, 26% of the population carry the gene; however, it is absent outside of Oceania. Black hair is the darkest hair color. It has large amounts of eumelanin and is more dense than other hair colors. Auburn hair ranges along a spectrum of light to dark red-brown shades. The chemicals which cause auburn hair are eumelanin (brown) and pheomelanin (red), with a higher proportion of red-causing pheomelanin than