ISSN:
0021-9541
Keywords:
Life and Medical Sciences
;
Cell & Developmental Biology
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Biology
,
Medicine
Notes:
Wild-type cultured cells of the frog cell line ICR 2A give rise to 5-bromodeoxyridine (BUdR)-resistant colonies only when the selecting concentration of the drug is 5 × 10-5 M or lower. The progeny of these colonies multiply in 10-4 M BUdR; resistance is correlated with the absence of a thymidine (TdR)-specific transport reaction with a Km in the range of 2-7 × 10-4 M. All of the TdR transport-deficient (TT-) isolates examined (25) had TdR kinase activity (4% to 100% of wild-type). Variants deficient in TdR kinase activity (5% of wild-type) were obtained by exposing TT-cultures to 10-3 M BUdR. The TK - variants multply continuously in 10-3 M BUdR and retain the phenotype after prolonged culture in the absence of the drug. The frequency with which they occur is increased 20 to 50 fold by prior treatment of the culture with ICR 191, an acridine mustard mutagen.In haploid cells, it would be expected that TK- variants would arise in equal numbers from wild-type and TT- cultures if loss TdR kinase occurred independently of loss of the transport reaction. However, wild-type cells give no colonies resistant to 10-3 M BUdR under conditions the give 1 to 50 colonies per million TT- cells. The TT- phenotype seems to be a required intermediate state in the origin of the TK- phenotype. Therefore, the TK- clones described above are unlikely to be products of mutation at a single genetic locus.
Additional Material:
7 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jcp.1040820208
Permalink
