An essentially full-length cDNA clone for the human enzyme monoamine oxidase 
type A (MAO-A) has been used to determine the chromosomal location of a gene 
encoding it. This enzyme is important in the degradative metabolism of biogenic 
amines throughout the body and is located in the outer mitochondrial membrane of 
many cell types. Southern blot analysis of PstI-digested human DNA revealed 
multiple fragments that hybridized to this probe. Using rodent-human somatic 
cell hybrids containing all or part of the human X chromosome, we have mapped 
these fragments to the region Xp21-p11. A restriction fragment length 
polymorphism (RFLP) for this MAOA gene was identified and used to evaluate 
linkage distances between this locus and several other loci on Xp. The MAOA 
locus lies between DXS14 and OTC, about 29 cM from the former.