Essentials of Genetics Study Set 1
Quiz 15 :
Regulation of Gene Expression
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Q17 Q17 Q17
(a) Describe by labeled diagram the structural components of the lac operon in E. coli. a() State the function of the lac regulator gene. b() State the function of fi -galactosidase in the lac system. c() Show by diagram the manner in which lactose brings about transcription of the three structural genes of the lac operon. d() Explain why certain mutations in the regulator gene (I -) of the lac system result in maximal synthesis of fi -galactosidase, permease, and transacetylase even in the absence of the inducer (lactose).
Q30 Q30 Q30
Regarding the trp operon, trpR - maps to a considerable distance from the structural genes. The mutation either inhibits the interaction with tryptophan or inhibits repressor formation entirely. In the presence of tryptophan in the medium, would you expect the trp operon to be transcriptionally active? Explain.
Q39 Q39 Q39
Mutagenic studies of the promoter region of the fi -globin gene indicate that some areas are more likely than mutations in other areas to affect transcription rates. When mutations occur in consensus sequences (modular elements such as GC box, CAAT box, TATA box), does transcription increase or decrease?