1. For E. coli strains with the following lac genotypes (a-d), use a plus sign (
ID: 3164465 • Letter: 1
Question
1. For E. coli strains with the following lac genotypes (a-d), use a plus sign (+) to indicate the synthesis of p galactosidase (from gene Z) and permease (from gene Y) and a minus sign (-) to indicate no synthesis of the protein:s when lactose is absent and when it is present. [24 pts lacP is the DNA promoter lacl encodes repressor protein lacY encodes the permease protein lacZ encodes the B-galactosidase protein lacO is the DNA operator region b. lacl lacP laco lacZ lacY a. lacl lacP laco lacZ lacY c. lacl lacP laco lacZ lacY e. lac# lacP laco lac? lacY/laci locp loco loc? locY f.laci lacP laco lacz lacY/loci lacP laco lacz locY d. lacl lacP laco lacz lacY/lacl lacP laco lacz lacY Lactose absent Lactose present B-galactosidase Perme Strain B-galactosidase Permease a. b. c. d. e.Explanation / Answer
For genotype lacI+ lacP+ lacO+ lacZ+ lacY+: All genes are working. Inducer is lactose. Therefore, in case of inducer absent; ?-galactosidase will not produced (-) because in absence of lactose lac repressor arrest lac operon for not producing the Permease enzyme. The mechanism bases on diauxe process if another substrate is present. Absent lactose = Permease enzyme will not produced (-); the reason is same as above given. Permease is the enzyme necessary for the permeation of lactose into cell.
Present lactose = both ?-galactosidase and Permease enzyme will produce (+) as all enzyme function normally.
For haploid strain:
Genotypes
Lactose present
Lactose absent
beta-galactosidase
Permease
beta-galactosidase
Permease
lacI+ lacP+ lacO+ lacZ+ lacY+
+
+
-
-
lacI+ lacP+ lacOc lacZ- lacy+
-
-
-
-
lacI+ lacP- lacO+ lacZ+ lacy-
-
-
-
-
lacI-/+ lacP+/+ lacO+/+ lacZ+/+ lacY+/+
+
+
-
-
lacIs/+ lacP+/+ lacO+/+ lacZ+/+ lacY+/+
+
+
-
-
lacI+/+ lacP+/+ lacO+/c lacZ+/+ lacY+/+
+
+
-
-
Genotypes
Lactose present
Lactose absent
beta-galactosidase
Permease
beta-galactosidase
Permease
lacI+ lacP+ lacO+ lacZ+ lacY+
+
+
-
-
lacI+ lacP+ lacOc lacZ- lacy+
-
-
-
-
lacI+ lacP- lacO+ lacZ+ lacy-
-
-
-
-
lacI-/+ lacP+/+ lacO+/+ lacZ+/+ lacY+/+
+
+
-
-
lacIs/+ lacP+/+ lacO+/+ lacZ+/+ lacY+/+
+
+
-
-
lacI+/+ lacP+/+ lacO+/c lacZ+/+ lacY+/+
+
+
-
-
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