Disclosed is a mammalian artificial chromosome vector which carries a humanchromosome-7 fragment containing human cytochrome P450 gene and which can betransmitted to progenies, wherein the human chromosome-7 fragment carriesa region containing at least a human CYP3A gene cluster located between chromosomemarkers AC004922 and AC073842 and having a size of about 1 Mb ± 500 Kb. Alsodisclosed is a non-human mammal which harbors the vector.