The rhesus macaque (Macaca mulatta), also called rhesus monkey. It is a typical diurnal macaque, common throughout Afghanistan to northern India and southern China. Rhesus macaques grow to a length of 64 centimetres, with tails reaching 30 centimetres. Males can weigh up to 6 kilograms, while females are around half that weight. They are brownish to grey in colour and have a pinkish face. Relatively easy to breed in captivity and because of its similarities to human anatomical and physiological traits, the rhesus monkey has often been used for medical or biological research, particularly for blood experiments. The rhesus monkey is most famous for the name it gave to a blood group system, due to an antigenic community between the monkey's red blood cells and human red blood cells. Its DNA sequence differs from that of humans by 7% and it has 21 pairs of chromosomes.