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Questions 29-32 LAC OPERON STRUCTURE Regulatory Promoter Operator Gene Structura

ID: 270061 • Letter: Q

Question

Questions 29-32 LAC OPERON STRUCTURE Regulatory Promoter Operator Gene Structural Genes lacZ lacY lacA The functions of the loci of the lac operon shown in the diagram are described in the table below Locus Function Attachment site for RNA polymerase Encodes a repressor protein that prevents transcription of the structural genes of the lac operon Attachment site for RNA polymerase lacl Operator Binding site for the repressor protein lacz lacy lacA Encodes beta-galactosidase, the enzyme that digests lactose to glucose and galactose Encodes lactose permease, the channel through which lactose moves into the cell Encodes galactoside transacetylase The diagram above represents a segment of the E coli chromosome that contains the laci gene and part of the lac operon, a coordinately regulated set of genes that are required for the metabolism of lactose. The presence of lactose, which causes the repressor to be released from the operator, results in increased transcription of the lac operon.

Explanation / Answer

29) B) Beta-galacosidase will be produced, even in the absence of lactose

Mutation in operation inhibits repressor protein from binding to it, resulting in the constitutive expression of structural genes

30) C) Expression of the Lac operon diminishes as lactose is depleted

31) D) The LacZ gene is highly expressed only when lactose is available

32) A) Bacteria growing in the presence of lactose will fluoresce under ultraviolet light.