Question 3 a)How does the structure of the lac operon ensure that the lac genes are coordinately controlled? Why would this be beneficial? The lac operon produces a polycistronic mRNA encoding three protein that all are important in lactose utilization. Having genes important to a single process regulated together is efficient way to ensure all need proteins are present when needed b)Describe the regulation of the lac operon (inducible, uniducible, or constitutive)in the case of each of the following mutants. In all cases the concentration glucose is low. Explain your hoice i)A mutation in the lac repressor such that it can t bind dNA constitutive ii)A mutation that makes lac permease nonfunctional umiducible iii)A mutant promoter that has a high affinity for polymerase iv) A mutant lac repressor that doesn t bind lactose inducible c) You have a cell where the expression of the lac operon is constitutive due to a mutation in the operator. If you add to that cell a completely wild-type version of the lac operon would normal regulation be restored? Explain cis. The Z, Y, and a genes attached to the mutant Operator region will always be constitutively/i No, normal regulation is not restored. Operators function at the dna level and thus can only act expressed 7012Fall2003Question 3 a) How does the structure of the lac operon ensure that the lac genes are coordinately controlled? Why would this be beneficial? The lac operon produces a polycistronic mRNA encoding three protein that all are important in lactose utilization. Having genes important to a single process regulated together is efficient way to ensure all need proteins are present when needed. b) Describe the regulation of the lac operon (inducible, uniducible, or constitutive) in the case of each of the following mutants. In all cases the concentration glucose is low. Explain your choice. i) A mutation in the lac repressor such that it can’t bind DNA constitutive ii) A mutation that makes lac permease nonfunctional uniducible iii) A mutant promoter that has a high affinity for polymerase inducible iv) A mutant lac repressor that doesn’t bind lactose uniducible c) You have a cell where the expression of the lac operon is constitutive due to a mutation in the operator. If you add to that cell a completely wild-type version of the lac operon would normal regulation be restored? Explain. No, normal regulation is not restored. Operators function at the DNA level and thus can only act in cis. The Z,Y, and A genes attached to the mutant Operator region will always be constitutively expressed. 7.012 Fall 2003 3