4. A number of mutations affect the expression of the lactose operon in E. coli
ID: 199078 • Letter: 4
Question
4. A number of mutations affect the expression of the lactose operon in E. coli a mutant lac repressor that cannot bind the lac operator S a mutant lac repressor that cannot bind lactose O a mutant lac operator that cannot bind repressor Lacl P a mutant lac promoter that cannot bind RNA polymerase a mutant lacZ with complete loss of -galactosidase activity Y a mutant permease with complete loss of the transporter activity Consider the following strains, each with the indicated mutations in the lac operon, would you expect high or low levels of -galactosidase activity in the presence of lactose? Please assume that there is no glucose present. (0.2 pt each, total 1 pt) 5. Would you expect the transcription of GAL1 to be high or low in galactose and in glucose medium in the following mutant strains? Please justify your conclusions (0.2 pt each, total 1 pt). a) Deletion of TATA box in the promoter of GAL1 b) Deletion of the UAS elements in the promoter of GAL1 c) Deletion of the GAL4 gene from the yeast genome d) Deletion of both GAL80 and GAL4 from the yeast genome e) Deletion of both GAL80 and MIG1 from the yeast genomeExplanation / Answer
in the absence of glucose bacteria utilised lactose by the use of Lac Operon.
Lac Operon produces enzyme beta galactosidase which is helpful in the production of glucose disaccharide lactose
for this enzyme production RNA polymerase binds to the promoter region and then do transcription of Beta galactosidase gene.
when the pressure molecule is present then it binds to the operator site and inhibit the formation of RNA .
operator and promoter are overlapping regions that's why binding of one inhibits binding of another.
when RNA polymerase binds to promoter beta galactosidase produce in high amount.
when operator parents with replaceable electricity is produced in very less amount.
when beta-galactosidase gene is mutated then zero production of Beta galactosidase enzyme.
permease allow the entry of lactose into cell. and after the entry of lactose repressor molecule is inactivated.
condition a: permease is mutated and repressor also mutated so continuous transcription and high amount of Beta galactosidase.
b and c:
both have mutation in operators so repressor cannot bind with operator in any condition so we can say beta galactosidase is produced in high amount.
d. permease is completely mutated so lactose cannot enter into the cell when lactose nit entering into the cell then repressor is highly active than zero rate of enzyme production.
e.
operator and permease is mutated so we can say basal level of enzyme production.
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