Aa Aa 1. Environmental conditions determine prokaryotic gene expression Escheric

Question

Aa Aa 1. Environmental conditions determine prokaryotic gene expression Escherichia coli bacteria use carbohydrates as a source of energy and amino acids (induding tryptophan) as building When it comes to amino adds, they can synthesize tryptophan but do so only when it is not available in their blocs for new proteins. As carbohydrates go, E. coli cells prefer glucose but will use lactose if glucose is unavailable. environment. E. coli cells can be grown with a variety of liquid and solid media. Consider a broth that contains lactose and tryptophan but lacks glucose. We'll abbreviate this medium as +lactose, -glucose, +tryptophan which of the following sets of proteins would an E. coli cell need to make for itself when cultured in the medium just described in bold? Check all that apply Lactose metabolism enzymes Tryptophan biosynthesis enzymes The following rectangle is a simplified representation of the E. coll chromosome. Within the chromosome are the trp and lac operons. Each operon contains a cluster of genes. The genes within the trp operon encode proteins required for tryptophan biosynthesis. The genes within the lac operon encode proteins required for lactose breakdown Determine which genes will be expressed when an E. coli cell is grown in this medium tro operon (contains five genes) lac operon (contains three genes) Type here to search F8 F10 F11 ±2@ 3£4¢5? 6? 7 I 82930v4 A?&

Explanation / Answer

The E. coli will synthesize only "lactose metabolism enzymes". Once the enzymes for lactose metabolism are synthesized, they will break down lactose into its monomer glucose and galactose. Since the medium already contains tryptophan, there is no requirement to synthesize the enzymes for tryptophan biosynthesis.

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