Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

Phenylalanine hydroxylase (PAH) and tyrosine hydroxylase (TH) are consecutive enzymes in the metabolic pathway leading to the production of catecholamine neurotransmitters. A comparison of recently available sequence data of these enzymes in the rat indicates about 70% homology in the 3' coding regions. We have localized TH by in situ hybridization to human chromosome region 11p15. Consideration of this assignment and that of PAH to chromosome 12, together with the known distribution of other pairs of related genes on these two chromosomes, provides convincing evidence of their ancestral relationship and suggests a role for gene duplication in the diversification of metabolic pathways in the vertebrate ancestors of mammals.

Original publication




Journal article


Cytogenet Cell Genet

Publication Date





29 - 32


Animals, Biological Evolution, Cells, Cultured, Chromosome Mapping, Chromosomes, Human, 6-12 and X, Female, Gene Amplification, Genes, Genetic Linkage, Genetic Markers, Humans, Hybrid Cells, Lymphocytes, Male, Mice, Nucleic Acid Hybridization, Tyrosine 3-Monooxygenase