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Question: A Muscle Enzyme Called ME Is Produced By Transcription And Translation Of The ME Gene In Several Muscles During Mouse Development, Including Heart Muscle, In A Highly Regulated Manner. Production Of ME Appears To Be Turned On And Turned Off At Different Times During Development. To Test The Possible Role Of Enhancers And Silencers In ME Transcription, ...

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ME1 ME1 LacZgene Upstream region Promoter A DI E LacZ activity (%) Deletion None (control) 100 A 100 B 100 c D <1 E 170 5 DelA muscle enzyme called ME is produced by transcription and translation of the ME gene in several muscles during mouse development, including heart muscle, in a highly regulated manner. Production of ME appears to be turned on and turned off at different times during development. To test the possible role of enhancers and silencers in ME transcription, a biologist creates a recombinant genetic system that fuses the ME promoter, along with DNA that is upstream of the promoter, to the bacterial lacZ ( galactosidase) gene. The lacZ gene is chosen for the ease and simplicity of assaying production of the encoded enzyme. The diagram shows the structure of the recombinant, as well as bars that indicate the extent of six deletions the biologist makes to the ME promoter and upstream sequences. The blue bar is the site of the promoter whereas the gray bars span potential enhancer/silencer modules. The table displays the percentage of galactosidase activity in each deletion mutant in comparison to the recombinant gene system without any deletions. a. Does this information indicate the presence of enhancer and or silencer sequences in the ME upstream sequence? If so, where is are the sequences located? b. Why does deletion D effectively eliminate transcription of lacZ? c. Given the information available from deletion analysis, can you give a molecular explanation for the observation that ME expression appears to turn on and turn off at various times during normal mouse development?

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