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Changes in DNA base sequence induced by gamma-ray mutagenesis of lambda phage and prophage
K R Tindall1, J Stein, F Hutchinson
1Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06511.
Genetics
|April 1, 1988
Summary
Gamma-ray irradiation of lambda phage and prophage DNA causes mutations. DNA repair mechanisms, like the SOS response, influence mutation types, including base substitutions and deletions, affecting phage and host genomes differently.
Area of Science:
- Molecular Biology
- Genetics
- Radiation Biology
Background:
- Gamma-ray irradiation is a known mutagen.
- Lambda phage and its integrated prophage form are distinct genetic systems.
- DNA repair pathways, such as the SOS response, modulate mutation outcomes.
Purpose of the Study:
- To characterize mutations induced by gamma-ray irradiation in lambda phage and prophage.
- To investigate the influence of host cell DNA repair mechanisms on mutation spectra.
- To compare mutation types in irradiated phage versus prophage.
Main Methods:
- Gamma-ray irradiation of lambda phage and prophage.
- Sequencing of 121 induced mutations.
- Assaying mutations in host cells with and without induced SOS response.
- Analysis of base substitutions, deletions, frameshifts, and gross rearrangements.
Main Results:
- In irradiated phage without SOS induction, G:C to A:T transitions predominated, potentially from deaminated cytosine mispairing.
- In irradiated phage with SOS induction, A:T substitutions were frequent, possibly from apurinic/apyrimidinic sites.
- Irradiated prophage showed both A:T and G:C substitutions, indicating host genome mutation mechanisms.
- Irradiated prophage also exhibited frameshifts and gross rearrangements.
Conclusions:
- Gamma irradiation induces diverse mutations in phage and prophage DNA.
- The SOS response significantly alters the mutation spectrum in irradiated phage.
- Prophage irradiation reveals distinct mutation mechanisms affecting both phage and host DNA, including G:C substitutions and larger genomic alterations.