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Title: DNA replication in Tetrahymena pyriformis
Author: Benhura, Mudadi Albert Nhamoinesu
ISNI:       0000 0001 3457 481X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 1979
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The effect of cytosine arabinoside on DNA synthesis in Tetrahymena pyriformis has been studied. DNA synthesis was determined by measuring the incorporation of (methyl-3H)thymidine into DNA. The DNA formed was analysed by sedimentation on alkaline sucrose gradients. In the presence of cytosine arabinoside labelled thymidine was incorporated into high molecular weight DNA. This indicates that in Tetrahymena, AraC inhibits the initiation steps of DNA synthesis but does not interfere with the elongation of DNA already formed. Initial experiments indicated that Tetrahymena quickly recovered from the effect of AraC. The metabolites of AraC were analysed by ion exchange chromatography. AraC was separated from AraCMP, AraCDP and AraCTP on the anion exchanger AG1-X8. AraC and AraU were separated on Dowex 50 or AG50-X8. It was found that whereas a large proportion of cellular AraC is converted to AraU only a small fraction is converted to AraCTP, the putative active agent in inhibiting DNA replication and causing cell death. In the presence of tetrahydrouridine AraC is not deaminated, but this did not lead to increased amounts of phos- phorylated products of AraC. Two DNA polymerase fractions which differed in their sensitivity to NEM and AraCTP were prepared. The nuclear enzyme was resistant to NEM and was activated by AraCTP. The cytoplasmic enzyme was inhibited by both AraCTP and NEM. An attempt was made to fractionate Tetrahymena DNA polymerases on DEAE-cellulose. Two fractions A and B, which differed in their ability to use polyA.polydT as a template-primer were prepared. The correspondence of these to in vivo nuclear and cytoplasmic enzymes is not yet clear.
Supervisor: Not available Sponsor: Association of Commonwealth Universities
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: QD Chemistry ; QL Zoology