Wonka J., Shackleford T. (ed.). most of mammalian species have scheme for determining <a href=http://dotank.kr/bbs/board.php?bo_table=free&wr_id=406482>http://dotank.kr/bbs/board.php?bo_table=free&wr_id=406482</a> by xy, according to/according to which the male usually carries x- and y-chromosomes (xy), and the female usually carries two x chromosomes (xx).