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Title: DNA secondary structure in vivo
Author: Davison, Angus
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 1994
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Long DNA palindromes cannot be propagated in wild-type Escherichia coli. Either a replicon with a long DNA palindrome is so poorly replicated that it is available, or the palindrome itself is unstable so that it undergoes partial or complete deletion. The deleterious effect of long DNA palindromes is alleviated in strains mutant for sbsC and D: each mutation by itself is necessary and sufficient to allow the plating of a λ phage containing a long palindrome. In this thesis, the mechanism by which long DNA palindromes cause inviability is studied, and it is discussed whether inviability is a consequence of an unusual DNA structure. An analysis of the effects of palindromic central asymmetry on the propagation of a λ phage across a broad range of E. coli host strains is described. Palindromes carrying an 8bp asymmetry confer a less severe phenotype than do perfect palindromes, arguing that a centre-dependent pathway for palindrome-mediated inviability exists that is independent of the host strain. For further study, a set of long DNA palindromes with paired changes in the central sequence was constructed in bacteriophage λ. Identical palindrome centres were previously used by others to test the S-type model for cruciform extrusion in vitro. The plaque areas produced by the palindrome-containing λ phage were compared on an E. coli sbsC lawn. Central sequence changes had a greater effect upon the plaque area than peripheral changes, implying that the residual palindrome-mediated inviability in E. coli sbcC is centre-dependent and could be due to the formation of a cruciform structure. The results argue strongly that intrastrand pairing within palindromes is critical in determining their effects in vivo.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available