Indicate the level of expression of the lac operon in the various mutants shown
ID: 279784 • Letter: I
Question
Indicate the level of expression of the lac operon in the various mutants shown in the table below (only relevant parts of the genotype are shown). You must answer in your answer book No lactose Lactose present Lactose present Escherichia coli genotype (no glucose) Glucose present No glucose none high 1. wildtype 2. lacP (affects lac operon promoter) 3. lacl 4. laclS 5. lacIS laco 6. laclacl S (partial diploid) 7. CAP gene 8. CAP gene- lacO ? 9. CAP genelacl 10. CAP gene I CAP gene Low (partial diploid)Explanation / Answer
E coli genotype No lactose Lactose/glucose Lactose/no glucose
2. lac P- none none none
3.lacI- (constitutively active mutant) high high high
4.LacIS (superrepressor of lacI) low low low
5.LacIS LacOc competition between superrepressor and constiutively active operator). Thus it depends upon the affect that LacIs has on operator. It will behave partial like wild type i.e with lactose expression will be moderate but with glucose, expression will be almost none.
6.LacI+LacS none none/low none/low as operator remains always repressed.
7.CAP- none none non/low as CAP enables RNA polymerase to bind and transcribe the genes
8.CAP gene-/lacOc none low none/low as CAP enables RNA pol to bind and if CAP gene is absent then no transcription takes place
9CAP gene-/lacOs none none/low none/low
10.CAP+ CAP- none low moderate to high