Northern blot analysis is performed on cellular mRNA isolated from E. coli. The probe used in the northern blot analysis hybridizes to a portion of the lacY sequence. Below is an example of the gel from northern blot analysis for a wild-type lac⁺ bacterial strain. In this gel, lane 1 is from bacteria grown in a medium containing only glucose (minimal medium). Lane 2 is from bacteria in a medium containing only lactose. Following the style of this diagram, draw the gel appearance for northern blots of the bacteria listed below. In each case, lane 1 is for mRNA isolated after growth in a glucose-containing (minimal) medium, and lane 2 is for mRNA isolated after growth in a lactose-only medium.
lac⁺ bacteria with the genotype I⁺ P⁺ Oᶜ Z⁺ Y⁺
Table of contents
- 1. Introduction to Genetics51m
- 2. Mendel's Laws of Inheritance3h 37m
- 3. Extensions to Mendelian Inheritance2h 41m
- 4. Genetic Mapping and Linkage2h 28m
- 5. Genetics of Bacteria and Viruses1h 21m
- 6. Chromosomal Variation1h 48m
- 7. DNA and Chromosome Structure56m
- 8. DNA Replication1h 10m
- 9. Mitosis and Meiosis1h 34m
- 10. Transcription1h 0m
- 11. Translation58m
- 12. Gene Regulation in Prokaryotes1h 19m
- 13. Gene Regulation in Eukaryotes44m
- 14. Genetic Control of Development44m
- 15. Genomes and Genomics1h 50m
- 16. Transposable Elements47m
- 17. Mutation, Repair, and Recombination1h 6m
- 18. Molecular Genetic Tools19m
- 19. Cancer Genetics29m
- 20. Quantitative Genetics1h 26m
- 21. Population Genetics50m
- 22. Evolutionary Genetics29m
12. Gene Regulation in Prokaryotes
Lac Operon
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Join thousands of students who trust us to help them ace their exams!Watch the first videoMultiple Choice
The lac operon encodes genes that are responsible for what?
A
Synthesizing more lactose
B
Breaking down lactose
C
Carrying lactose to the mitochondria
D
Converting lactose into cellulose

1
Understand the function of the lac operon: The lac operon is a set of genes found in E. coli and other bacteria that are involved in the metabolism of lactose.
Identify the components of the lac operon: It includes three structural genes (lacZ, lacY, and lacA), a promoter, a terminator, and an operator.
Determine the role of each gene: The lacZ gene encodes β-galactosidase, which breaks down lactose into glucose and galactose. The lacY gene encodes permease, which facilitates the entry of lactose into the cell. The lacA gene encodes transacetylase, which is involved in the removal of toxic by-products of lactose digestion.
Recognize the regulatory mechanism: The lac operon is regulated by the presence or absence of lactose. In the absence of lactose, a repressor binds to the operator, preventing transcription. When lactose is present, it binds to the repressor, causing a conformational change that releases the repressor from the operator, allowing transcription.
Conclude the primary function: The lac operon is primarily responsible for breaking down lactose into simpler sugars that can be used by the cell for energy, not for synthesizing more lactose or converting it into other substances.
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