The ilv-leu operon of bacillus subtilis comprises seven genes necessary for the biosynthesis of isoleucine, valine, and leucine. the structural genes of this operon are transcribed when these amino acids are deficient in the cell. the vana operon codes enzymes that modify the binding targets of antibiotic vancomycin and therefore give antibiotic resistance to the bacteria. the structural genes of this operon are transcribed when the antibiotic vancomycin is present in the environment. the ilv-leu operon is operon, and the vana operon is operon.

The ilv-leu operon is a repressible operon.

The Van A operon is a Inducible operon.

An operon is a genetic unit of coordinated expression. It comprises a group of adjacent structural genes encoding the enzymes of the same metabolic pathway, as well as the regulatory sequences affecting the transcription of these structural genes.

The mRNA resulting from this set is synthesized in a single block called polycistronic RNA.

These operons are submitted via effector molecules either to an inducing modulation or to a repressive modulation.

igneous rocks are formed by solidification of cooled magma (molten rock), with or without crystallization, either below the surface as intrusive (plutonic) rocks or on the surface as extrusive (volcanic) rocks.  

the composition depends on the source magma. there are almost a thousand types of composition found till now.  

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