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
Problem 20a
Textbook Question
Suppose each of the genotypes you listed in parts (a) and (b) of Problem 19 are placed in a partial diploid genotype along with a chromosome that has a fully wild-type lac operon.
Which partial diploids will be able to grow on a lactose medium?

1
Identify the genotypes listed in parts (a) and (b) of Problem 19. These genotypes will be used to create partial diploids with a wild-type lac operon.
Understand the components of the lac operon: the promoter (P), operator (O), and the structural genes (lacZ, lacY, lacA). The wild-type operon can express these genes in the presence of lactose.
Determine the functionality of each genotype in terms of the lac operon components. Consider mutations that might affect the operon's ability to utilize lactose, such as mutations in the operator (O^c), promoter (P^-), or structural genes (lacZ^- or lacY^-).
For each partial diploid, assess whether the presence of the wild-type lac operon can complement any defective components in the other genotype. This involves checking if the wild-type operon can provide functional copies of any non-functional components.
Conclude which partial diploids have at least one functional lac operon that can be induced by lactose, allowing the bacteria to grow on a lactose medium.
Recommended similar problem, with video answer:

This video solution was recommended by our tutors as helpful for the problem above
Video duration:
1mPlay a video:
Was this helpful?
Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
Lac Operon
The lac operon is a set of genes in E. coli that are responsible for the metabolism of lactose. It consists of structural genes (lacZ, lacY, and lacA) that encode proteins necessary for lactose uptake and breakdown. The operon is regulated by the presence of lactose and glucose, allowing the bacteria to efficiently use lactose when glucose is scarce.
Recommended video:
Guided course
Lac Operon Overview
Partial Diploidy
Partial diploidy refers to a genetic condition where a bacterium contains two copies of some genes, typically due to the introduction of a plasmid or another chromosome. In the context of the lac operon, this means that the bacterium can express genes from both its own chromosome and an introduced chromosome, which can affect its ability to metabolize lactose depending on the alleles present.
Recommended video:
Guided course
Diploid Genetics
Lactose Medium Growth
Growth on lactose medium indicates that a bacterium can utilize lactose as its sole carbon source. For this to occur, the bacterium must have functional genes for the lac operon, allowing it to transport and metabolize lactose. The ability to grow on lactose medium is a key indicator of whether the lac operon is expressed and functional in the given genetic context.
Recommended video:
Guided course
Lac Operon Summary
Watch next
Master Lac Operon Overview with a bite sized video explanation from Kylia Goodner
Start learning