Sequences on the human Y chromosome homologous to the autosomal gene for argininosuccinate synthetase

We have used a probe (pAS-1) to the human urea cycle enzyme argininosuccinate synthetase (AS) to detect individual variation in restriction enzyme digests of human DNA from lymphocytes, fibroblasts and transformed cell lines (including HeLa). pAS-1 is a 1.55 kilobase (kb) sequence of cDNA from poly(A) + RNA cloned in pBR322; it represents more than 90% of the AS message 1 . At least 15 genomic fragments are detected with pAS-1 in DNA digested with restriction enzymes recognizing 6-base sequences 2 . This multiplicity of fragments is explained in part by the observation that AS-like sequences are found on more than seven human chromosomes 3 . We report here population data and gene dosage experiments demonstrating an AS-like sequence on the human Y chromosome and confirming an AS-like sequence on the human X chromosome.