George E. Holmes

• EDUCATION PhD
• Professor (Associate) at Howard University

DNA damages occur continuously in cells of living organisms. While most of these damages are repaired, some accumulate. In particular, there is evidence for DNA damage accumulation in non-dividing cells of mammals. These accumulated DNA damages probably interfere with RNA transcription. We consider that the decline in the ability of DNA to serve as...

Paramecium tetraurelia cells of ages 4, 15, and 27 days were labeled with [14C]-thymidine. In addition, cells were grown clonally for 27 days (108 generations) and labeled with [14C]-thymidine in the presence of 0.5 or 7.5 micrograms/ml of mitomycin-C (MMC) or no MMC. These cells were gently deposited on a filter membrane, which impedes the passage...

The accumulation of DNA fragments in aging Paramecium tetraurelia after 15 days (or approximately 60 generations) of clonal growth in both axenic and nonaxenic media was assayed by alkaline elution assay. This sensitive technique permits measurement of single-strand breaks in double-stranded DNA. The results obtained indicate that P. tetraurelia ag...

Treatment of phage T4-host adsorption complexes with mitomycin C (MMC) doubled the frequency of recombination between two rII markers. The rate at which MMC delivered lethal lesions to cells infected by two or more phage (multicomplexes) was 10-fold less than the rate at which they were delivered to singly infected cells (monocomplexes). Thus there...

A temperature sensitive ligase allele of phage T4 reduced or eliminated HNO2 induced reversion of am mutants. Since at the temperatures used, the ligase mutant is defective in the repair of some types of lethal lesions (i.e., UV, MMS and EMS induced lesions) these results indicate that HNO2 mutagenesis may occur through a ligase dependent repair pa...

were shownbyinvivoandinvitro experiments toparticipate inbothpositive and negative intragenic complementation. Thisarguesthatincomplete polypeptide chains canparticipate insubunit interaction. ChiuandGreenberg (4)haveobserved intra- genic complementation intsx tsmixedinfec- tions byusing tsmutants defective ingene42of phage T4,thegenethat specifies...

BECKWITH and Scaife1,2 showed that the suppressor allele suA of Escherichia coli does not suppress nonsense codons in the lactose operon, but does relieve the polarity effect of UAG, UAA and possibly frameshift mutations. It is shown here that suA E. coli strongly suppresses phage T4 amber mutations and weakly suppresses phage T4 temperature-sensit...