We describe the genetic mapping of hyperphenylalaninemia 2 (hph2), a r
ecessive mutation in the mouse that causes deficient amino acid transp
ort similar to Hartnup Disorder, a human genetic amino acid transport
disorder. The hph2 locus was mapped in three separate crosses to ident
ify candidate genes for hph2 and a region of homology in the human gen
ome where we propose the Hartnup Disorder gene might lie. The mutation
maps to mouse Chromosome (Chr) 7 distal of the simple sequence length
polymorphism (SSLP) marker D7Mit140 and does not recombine with D7Nds
4, an SSLP marker in the fibroblast growth factor 3 (Fgf3) gene. Unexp
ectedly, the mutant chromosome affects recombination frequency in the
D7Mit12 to D7Nds4 interval.