The trp operon in e. coli regulates genes that code for enzymes required for synthesis of the amino acid tryptophan. the trp operon is a repressible operon. when tryptophan is not available in the environment, the trp repressor protein is . therefore, rna polymerase can bind to to begin transcription first blank ,actve, inactive or regulated second blank operator, prometer, or structual genes

Ans.

Try operon or tryptophan operon represents a cluster of genes that transcribe together to code enzymes for tryptophan production. The try operon is regulated by a repressor protein. When tryptophan is present, it activates repressor protein that binds to operator and prevent expression of genes.

In the absence of tryptophan, repressor protein is present in inactive form that cannot bind to the operator. Therefore, RNA polymerase binds to promoter region and genes for tryptophan synthesis get expressed.

Thus, the correct option to be fill in the first blank is 'inactive or regulated' and for the second blank is 'promoter.'

answer: the blood-brain barrier is a layer of specialized membranes and cell processes designed to keep undesirable substances from passing from the bloodstream into the precious tissues of the brain. while the blood-brain barrier does keep most bad things out of the central nervous system, it is not impermeable.

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