Synthesis of Repair Proteins Is Regulated

coli the synthesis of many enzymes involved in repair is regulated by the so-called SOS system. Two proteins, lexA and recA, form the working machinery of this regulatory system (fig. 26.19). Under normal conditions the lexA protein inhibits the expression of about 17 genes (the din genes), the encoded proteins of which are 

Individuals belonging to the same species carry approximately the same number of genes positioned in the same relative locations on their homologous chromosomes each gene is represented by more than one variant which frequently results in different visible characteristics (phenotypes) in different individuals. The different representations 

Meselson model for phage recombination (circa 1964). Phage form staggered breaks. Base pairing leads to an annealed complex with gaps. Gaps are mended by repair synthesis. 

Genetic investigations have supported the Holliday model and at the same time indicate that different organisms can only be explained by variations of the model. 

Enzymes Have Been Found in Escherichia coli That Mediate the Recombination 

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