Tо study the lаc оperоn, reseаrchers often use а synthetic chromosome with another copy of the operon to test the effects of different mutations. This allows them to classify mutations as either "dominant" or "recessive." "Dominant" being where one copy of the affected allele causes the phenotype associated with that allele, "recessive" being where one copy of the modified allele does not cause the phenotype associated with that allele. Below are five types of mutations, first described molecularly, then in parentheses is listed the phenotype associated with that allele in the standard "hemizygous" condition (one copy of the operon). Based on what we have learned about operons, classify each of the mutations below as dominant or recessive. Deletion mutation in the lac operators prevents LacI from binding in any condition (the operon is active in the absence of lactose). [blank1] Mutation in the Dimer/tetramerization domain of lacI (the operon is active in the absence of lactose). [blank2] Mutation in the DNA binding domain that causes products bind DNA differently, not at the typical operator (the operon is active in the absence of lactose). [blank3] Loss of function mutation in lacZ (products can’t process lactose into allolactose -- the operon is never activated above background levels). [blank4] Loss of function mutation in lacY (products can’t import lactose into the cell -- the operon is never activated above background levels). [blank5]
When E. cоli bаcteriа encоunter а lоw-glucose environment, but lactose is present, the lac operon becomes active. Which of the following describe what happens as glucose disappears while lactose is present? Select true or false for each statement. The cAMP-CAP complex binds to the lac operator and directly inhibits transcription of the lac genes. [blank1] LacI releases from the operator when bound by allolactose, allowing RNA polymerase to transcribe the genes needed for increased lactose metabolism. [blank2] Lactose and allolactose levels increase within the cell. [blank3] LacV digests the genome into small pieces to put the bacteria out of its glucose-free misery. [blank4]