The twins were asked whether their hair was curly, wavy or straight, and their answers were matched with data about their genomes by scientists from the Queensland Institute of Medical Research (QIMR) Genetic Epidemiology Laboratory. Two and a half million single nucleotide polymorphisms (SNPs) were examined and the results showed variation of the TCCH gene on chromosome one.
People with curly hair shared the same genetic variation of the TCCH gene and there was also a genetic variation shared by people with straight hair. Biologically the curliness of hair is determined by the distribution of proteins called keratins as well as cell types in the hair fibre. As hair becomes curlier the number of mesocortical cells decreases.
However, it is not known how the variation contributes to the different natural hair styles. One idea is that an alteration of the gene could lead to an amino acid change in the TCCH protein which in turn influences how straight or how curly hair will appear to be.
