An operon is a cluster of co-ordinately regulated genes. It includes structural genes (enzymes), regulatory genes (activators or repressors), and regulatory sites such as promoters and operators. Consider the following situation of operon.Regulatory element is present ----------- Operon ONMutation of Regulatory gene to lose function -------------- Operon OFFWhich of the following given statements is correct regarding this type of regulation? Genes in this operon are expressed unless they are switched off by a repressor protein The inactivation of the repressor shall lead to the turning on of the operon The absence of positive regulatory protein shall lead to turn off of the operon The inactivation of the repressor shall lead to the turning off of the operon

Read the following and answer any four questions: Gene regulation is the mechanism of switching off and switching on of the genes depending upon the requirement of cells and the state of development. Gene regulation is of two types: negative and positive. In negative gene regulation, the genes continue expressing their effect till their activity is suppressed. Positive gene regulation is the one in which the genes remain non - expressed unless and until they are induced to do it. Operon model is a co - ordinated group of genes such as structural gene, operator gene, promoter gene, regulator gene which function together and regulate a metabolic pathway as a unit, e.g., lac operon, trp operon, ara operon, etc. 1. Regulation of gene expression occurs at the level of: a. transcription b. processing/splicing c. translation d. all of these An inducible operon system usually occurs in A pathway. Nutrient molecules serve as B to stimulate the production of the enzymes necessary for their breakdown. Genes for inducible operon are usually switched C and the repressor is synthesised in an D form. 2. An mRNA molecule transcribed from the lac operon contains nucleotide sequences complementary to a. structural genes coding for the enzymes b. the operator region c. the promotor region d. the repressor gene. 3. Which statement correctly describes the control of transcription of the genes involved in the breakdown of lactose in Escherichia coli? a. A repressor protein binds to the operator and the genes are switched on. b. A repressor protein binds to the operator and the genes are switched off. c. A transcription factor binds to the promoter and the genes are switched on. d. A transcription factor binds to the promoter and the genes are switched off. 4. Function of catabolic activator protein in lac operon is: a. to form mRNA b. help to bind RNA polymerase c. code for repressor d. to activates lac gene when glucose is absent 5. In eukaryotes, the regulation could be exerted at a. transcriptional level (formation of primary transcript) b. processing level (regulation of splicing) c. transport of mRNA from nucleus to the cytoplasm all of these

What is the relationship between a gene and an operon?Group of answer choicesAn operon is a group of bacterial genes that share a common promoterAn operon is a bacterial gene that must have activation and repressionEvery bacterial gene is part of an operonAn operon is any bacterial gene

Which of the following would not be a component of an operon?ANSWERPromoterStart codonOperatorStructural genes

In an operon, the regulator and operator genes are notassociated with the constitutive genes.Reason (R) : Constitutive genes need not be repressed.(a) Both Assertion (A) and Reason (R) are true and Reason (R) is thecorrect explanation of the Assertion (A).(b) Both Assertion (A) and Reason (R) are true, but Reason (R) is notthe correct explanation of the Assertion (A).(c) Assertion (A) is true, but Reason (R) is false.(d) Assertion (A) is false, but Reason (R) is true.

Which of the following is not induced in the operon model?Group of answer choicesregulator geneoperatorrepressorstructural genenone of the above