Abstract
4-Nitroquinoline 1-oxide (4NQO) is known to induce respiration-deficient (RD) mutants in yeast. We have investigated some physico-chemical properties of mitochondrial DNA in several clones of RD mutants which had been isolated at various time periods of 4NQO treatment. The buoyant densities of all RD mutants DNA's were reduced, and those mitochondrial DNA showed reversible and simple melting profile and had lower melting temperature. In contrast with RD mutants, melting profile of normal yeast mitochondrial DNA was broad and asymmetric and markedly different from that of the DNA's from RD mutants. Chemical analysis of base composition in mitochondrial DNA showed considerable reduction of guanine-cytosine contents. Possible mechanisms in RD mutagenesis by 4NQO are discussed.
