In 1955–1956 he was House Physician and House Surgeon at the
Western Infirmary in Glasgow and in 1956–1958
Senior House Officer (SHO) and Registrar in
Pathology.
Johns Hopkins In 1959 he was appointed a
Fellow in Medicine at the School of Medicine,
Johns Hopkins University,
Baltimore where he worked on
chromosome analysis for nearly three years, establishing the first
human chromosome diagnostic laboratory in the USA.
Return to Glasgow In 1961 he returned to the Department of
Genetics at the University of Glasgow and was appointed Lecturer, Senior Lecturer and Reader successively, becoming the first Burton Professor of Medical Genetics in 1973. Apart from teaching genetics to
medical students, his duties involved the establishment of a Regional Genetics Service for the West of Scotland. This provided opportunities for contributing to the
human gene map using familial chromosome
polymorphisms,
deletion mapping,
in situ hybridisation and chromosome sorting by
flow cytometry. His work on mapping the
Y-linked sex determinant in
XX males led to the isolation of the mammalian sex-determining gene twenty-five years later.
Gene mapping In 1987 he was appointed Professor and Head of the
Department of Pathology at
University of Cambridge and Director of the East Anglia Regional Genetics Service, where he furthered his research on
gene mapping. He retired as Head of Pathology in 1998 and moved to the University Department of Veterinary Medicine. In 2002 he established the Cambridge Resource Centre for Comparative Genomics which produced and distributed chromosome-specific
DNA from over 120 species of animals, birds and fish to scientists worldwide for research in
biology,
evolution and gene mapping. This data allowed comparisons between species to be made and mapped, illuminating the relationships between species and allowing research into genomic evolution. ==Personal life and death==