1. The concepts covered here can be reviewed in your textbook, pages 232-235, and your lecture notes.
2. In conjugation, a plasmid is transferred from one bacterium to another via a pilus. Review the process of conjugation and answer the following questions:
- How many bacteria are required for conjugation to occur?
- Is contact between the bacteria required, and if so, how is it achieved?
- What do we mean when we say that two bacteria are of opposite mating types?
- What are F+, F-, Hfr cells?
- Describe the process of the transfer - is the plasmid replicated before transfer, what is transferred, is it ss or dsDNA, etc. Answer this question in a paragraph form
- Make a diagram of the transfer between an F+ and an F- cell
3. The F plasmid is replicated using sigma, or rolling circle replication. On a piece of paper answer the following questions:
- How many origins of replication does the F plasmid have?
- How many replication forks are produced during rolling circle replication?
- How is the replication of the D plasmid times relative to its transfer?
- After studying your lecture notes, make a diagram of the rolling circle replication (without looking at your notes). Label a few genes on your diagram and show their positions throughout the replication making sure they are in the right place relative to the origin of replication.
4. In Hfr cells, the F plasmid is inserted randomly in the chromosome. Below is the chromosome of an Hfr cell, with the F plasmid inserted in it and some genes.
- Draw a diagram of the rolling replication of the F plasmid in this Hfr cell (similar to the diagram you drew in point 3 above).
- Order the genes based on their likelihood of being transferred to the donor, starting from the most likely to the least likely. Why did you order them like that?
5. If you feel that you have mastered the concepts on this page, you can move to the next sub-unit, which explores viruses.