Summarize the arguments for and against patenting genetically modified organisms.
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
18. Molecular Genetic Tools
Genetic Cloning
Problem 15a
Textbook Question
The bacteriophage lambda genome can exist in either a linear form or a circular form.
How many fragments will be formed by restriction enzyme digestion with XhoI alone, with XbaI alone, and with both XhoI and XbaI in the linear and circular forms of the lambda genome?

1
Step 1: Understand the lambda genome structure. The bacteriophage lambda genome can exist in two forms: linear and circular. In the linear form, the genome has free ends, while in the circular form, the ends are joined to form a loop. This structural difference affects how restriction enzymes cut the DNA.
Step 2: Learn about the restriction enzymes XhoI and XbaI. Restriction enzymes recognize specific DNA sequences and cut at those sites. For example, XhoI recognizes the sequence 5'-CTCGAG-3', and XbaI recognizes the sequence 5'-TCTAGA-3'. The number of fragments produced depends on the number of recognition sites in the genome.
Step 3: Determine the number of recognition sites for XhoI and XbaI in the lambda genome. This information is typically provided in the genome map or sequence data. Count the number of sites for each enzyme in both the linear and circular forms of the genome.
Step 4: Analyze the cutting pattern for each enzyme. In the linear form, each recognition site results in a cut that produces two fragments. In the circular form, the genome is a loop, so the number of fragments produced is equal to the number of cuts made by the enzyme.
Step 5: Combine the effects of both enzymes. When both XhoI and XbaI are used together, the total number of fragments is determined by the combined number of cuts made by both enzymes. Consider how overlapping recognition sites (if any) might affect the fragment count in both linear and circular forms.

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.
Bacteriophage Lambda Genome Structure
The bacteriophage lambda genome can exist in two forms: linear and circular. The linear form is typically found during the infection process, while the circular form can occur after the genome is integrated into the host's DNA. Understanding these forms is crucial for predicting how the genome will behave during restriction enzyme digestion.
Recommended video:
Guided course
Bacteriophage Life Cycle
Restriction Enzymes
Restriction enzymes, such as XhoI and XbaI, are proteins that cut DNA at specific sequences. XhoI recognizes the sequence CTCGAG, while XbaI recognizes the sequence TCTAGA. The number of fragments produced by digestion depends on the number of recognition sites present in the DNA, which varies between the linear and circular forms of the genome.
Recommended video:
Guided course
Mapping with Markers
DNA Fragmentation and Analysis
When a DNA molecule is cut by restriction enzymes, it is fragmented into smaller pieces. The number of fragments generated can be calculated based on the number of cutting sites. In the case of the lambda genome, analyzing the resulting fragments from different enzyme combinations helps in understanding the genome's structure and the effects of the enzymes used.
Recommended video:
Guided course
Chi Square Analysis
Related Videos
Related Practice
Textbook Question
948
views