Plasmid Transfer and Conjugation
Donor and Recipient Cell Interaction
- Plasmids are small DNA fragments separate from the main chromosome.
- They carry genetic information, such as antibiotic resistance.
- The initial step in plasmid transfer involves contact between the donor and recipient cells.
- Pili of the donor cell recognize and bind to specific receptor sites on the cell wall of the recipient cell.
Plasmid Mobilization
- The plasmid becomes mobile for transfer.
- An enzyme cleaves one strand of the plasmid at a specific nucleotide sequence.
- This sequence is called the origin of transfer.
DNA Transfer
- A single strand of the plasmid, starting at the origin of transfer, enters the recipient cell.
Synthesis of Complementary Strand
- Once inside the recipient cell, a complementary strand to the transferred DNA is synthesized.
Cell Conversion
- When donor and recipient cells are mixed, all cells eventually behave like donors.
Conjugation Defined
- Conjugation is a gene transfer mechanism requiring direct contact between donor and recipient cells.
Detailed Steps of Plasmid Transfer
- A plasmid is a small piece of DNA, separate from the main chromosome, carrying genetic information (e.g., antibiotic resistance).
- The first step is contact between donor and recipient cells.
- Pili from the donor cell recognize and bind to specific receptor sites on the recipient cell wall.
- The plasmid is then mobilized for transfer.
- An enzyme cleaves one strand of the plasmid at a specific nucleotide sequence called the origin of transfer.
Recipient Cell Integration
- A single strand of the plasmid, beginning at the origin of transfer, enters the recipient cell.
- Inside the recipient cell, a complementary strand to the single DNA strand is synthesized.
- When donor and recipient cells are mixed, eventually all cells behave like donors.
