Thymidine kinase activity and human chromosome No. 18

Somatic cell hybridization studies have suggested that the locus for human thymidine kinase is on a No. 17 or No. 18 chromosome. To evaluate further this possibility, fibroblast cell cultures from patients with partial monosomy 18 and trisomy 18 were assayed for thymidine kinase activity; the enzyme levels in these cell extracts were normal. If the enzyme activities reflect a simple gene dose effect, these results suggest that the human thymidine kinase locus is not situated on the No. 18 chromosome.Supported in part by Grant # MR 0504A-69 from the Division of Mental Retardation, Social and Rehabilitation Service, Department of Health, Education and Welfare, and by the Institute of Child Health and Human Development, Grant # DO 4612, Mental Retardation Research Center, UCLA/NPI.