Fill in the table describing the expression of B-gal and lac permease, as well a
ID: 16391 • Letter: F
Question
Fill in the table describing the expression of B-gal and lac permease, as well as the overall lac phenotype for the following strains. A lac+ phenotype is defined as the ability to grow on lactose-only plates (i.e. there must be B-gal and permease produced). The first two rows are filled in:
B-galactosidase (Z) Lac Permease (Y) Lac+?
expression expression
1. I+ P+ O+ Z- Y+ none inducible -
2. I+ P+ Oc Z+ Y- constitutive none -
3. Is P+ O+ Z+ Y+
4. I- P+ O+ Z+ Y-
5. Partial diploid 1+2
6. Partial diploid 2+3
7. Partial diploid 3+4
8. Partial diploid 1+4
Explanation / Answer
B-galactosidase (Z) Lac Permease (Y) Lac+?
expression expression
1. I+ P+ O+ Z- Y+ none inducible -
2. I+ P+ Oc Z+ Y- constitutive none -
3. Is P+ O+ Z+ Y+ uninducible inducible -
4. I- P+ O+ Z+ Y- constitutive none -
5. Partial diploid 1+2 constitutive inducible +
6. Partial diploid 2+3 constitutive inducible +
7. Partial diploid 3+4 uninducible inducible -
8. Partial diploid 1+4 inducible inducible +
For 3 Is means super repressor so it its uninducible which means that even in the presents of an inducer no lac mRNA will be synthesized
I'm assuming that one of the plasmids are an F ' while the other is the chromosome. The thing to remember is that lacOc is only constitutive if the lacOc and the lacZ+ allele sare on the same DNA molecule. Another thing to remember is that P- and lacOc are not complemented which means that a wildtype version of them will not be able to hijack the system in order to make the protein function normal again.
Hopefully this helps...
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