Mutations

Human Gene Mutations

Mutations     

Mutations inPisum

Molecular Genetics and Genomics -     

Enriched Selection of Dominant Mutations: Histidine Operator Mutations

In the course of selection of bacteria with derepressed levels of histidine biosynthetic enzymes, it was found that when mutagen-treated cells were spread on a selective medium without allowing intervening growth to occur, the frequency of operator mutants obtained was dramatically increased. This may be useful as a general enrichment for operator or other dominant mutations.     

Genetic Analysis of Mutations Indirectly Suppressing recB and recC Mutations

Mutations in sbcB inactivate exonuclease I and suppress the UV-sensitive, mitomycin-sensitive, recombination-deficient phenotypes associated with recB and recC mutations. Mapping experiments have located sbcB about 0.4 minutes from the his operon at 38.0 on the standard map of E. coli. This places sbcB between supD and his. A four-point cross shows that sbcB lies between P2 attH and his. P2 eduction deleting the his operon beginning with P2 attH also deletes sbcB and produces the expected exonuclease I deficiency and suppression of recB(-). The occurrence of chemical-mutagen-induced and spontaneous mutations indirectly suppressing recB(-) and recC(-) is examined. Three lines of strains produce only sbcA mutations while only sbcB mutations occur in a fourth line. Explanations for this behavior are proposed in light of the ability of the first three lines to express sbcB mutations which they inherit by transduction.     

Mutations in rDNA

Summary The action of -amanitin, an inhibitor of RNA synthesis, on the induction by hydroxyurea (HU) of chromosomal aberrations in nucleolus organizer regions of barley was studied. The data obtained show that -amanitin can effectively modify aberration induction in rDNA. Administered before mutagen treatment or in combination with the mutagen, the toxin significantly decreased the HU-induced aberration frequencies in NORs. The data obtained provide further evidence that -amanitin is an effective modulator of aberration induction in NORs either by interfering with RNA synthesis or by modifying chromatin structure.