Can you explain to me this Q ?? and what does lactose present and absent mean? F
ID: 227296 • Letter: C
Question
Can you explain to me this Q ?? and what does lactose present and absent mean?
For E. coli strains with the lac genotypes shown below, use a plus sign (+) to indicate the production of beta-galactosidase and permease and a minus (-) sign to indicate no production of the proteins.
Genotype of haploid strain; Lactose absent / Lactose present for beta-galactosidase and Permease. lacI+ lacP+ lacO+ lacZ+ lacY+
lacI- lacP+ lacO+ lacZ+ lacY+
lacI+ lacP+ lacOc lacZ+ lacY+
lacI- lacP- lacO+ lacZ+ lacY+
Genotype of partial diploid strain; Lactose absent / Lactose present for beta-galactosidase and Permease.
lacI+ lacP+ lacO+ lacZ- lacY+ / lacI- lacP+ lacO+ lacZ+ lacY-
lacI- lacP+ lacOc lacZ+ lacY+ / lacI+ lacP+ lacO+ lacZ- lacY-
lacI- lacP+ lacO+ lacZ+ lacY- / lacI+ lacP- lacO+ lacZ- lacY+
lacI+ lacP- lacOc lacZ- lacY+ / lacI- lacP+ lacO+ lacZ+ lacY-
lacIs lacP+ lacO+ lacZ+ lacY- / lacI+ lacP+ lacO+ lacZ- lacY+
Explanation / Answer
Here we have to find whether enzymes beta-galactosidase and permease will produce in the presence or absence of Lactose with concerning each genotype.
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+ lacO+ lacZ+ lacY
+
+
+
+
lacI+ lacP+ lacOc lacZ+ lacY+
+
+
+
+
lacI- lacP- lacO+ lacZ+ lacY+
+
-
+
-
In case of diploid strain, if one of two chromatids has positive allele, then the genotype will function normally.
For example
lacI+ lacP+ lacO+ lacZ- lacY+ / lacI- lacP+ lacO+ lacZ+ lacY-
Lactose present: beta-galactosidase and permease will produce because at least one positive or functional allele present in the genotype. Here lacZ- show mutation in one chromosome but it is present in its complementary.
Genotypes
Lactose present
Lactose absent
beta-galactosidase
Permease
beta-galactosidase
Permease
lacI+ lacP+ lacO+ lacZ+ lacY+
+
+
-
-
lacI- lacP+ lacO+ lacZ+ lacY
+
+
+
+
lacI+ lacP+ lacOc lacZ+ lacY+
+
+
+
+
lacI- lacP- lacO+ lacZ+ lacY+
+
-
+
-
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