 Its gene locus is on the short arm of chromosome 9 in humans, and on a corresponding location on chromosome 4 in mice.It is located near the genes for the tandem repeats INK4a and INK4b, which are 16 kDa (p16INK4a) and 15 kDa (p15INK4b) proteins, respectively.These INK4 proteins directly inhibit the cyclin D-dependent kinases CDK4 and CDK6.