Plasmids | Genetics | Biology

Bacteria play a crucial role in genetic engineering.
They provide:
- Restriction Enzymes: These enzymes cut DNA at specific sequences.
- Plasmids: Small, circular DNA molecules that exist alongside the bacterium's single chromosome.

Size: Typically range from 1,000 to 100,000 nucleotides long.
Function: They act as independent, self-replicating molecular operators within bacteria.
Genetic Recombination: Plasmids facilitate the transfer of genetic traits between bacteria, beyond what is encoded in the chromosome.
Example: Some plasmids carry genes that code for enzymes to digest antibiotics, providing a survival advantage to bacteria.
- When a bacterium with such plasmids dies, it releases the plasmids into the environment, where they can be acquired by other bacteria.

Restriction Enzymes: Used to cut plasmids and insert desired gene segments.
Joining DNA: Repair enzymes are added to join the DNA fragments at their sticky ends.
Transformation: New plasmids with inserted genes are introduced to bacteria.
Culture Growth: Bacteria are grown in a solution that helps plasmids penetrate their cell walls and membranes.
- Not all bacteria will absorb the new plasmids.
Selection and Purification:
- Bacteria are exposed to antibiotics (like ampicillin and amoxicillin) to kill those that did not uptake the plasmids.
- Surviving bacteria are those that have absorbed plasmids providing antibiotic resistance, along with the inserted genes (e.g., for insulin or growth hormones).
- The cultured bacteria are harvested for the production of recombinant proteins for human use.

Two methods for DNA insertion into complex organisms (plants and animals):
- Vector Methods: Do not require a third organism for DNA transfer.
- Vectors: Organisms or systems used to carry DNA from one species and insert it into another.

Genetic engineering technology harnesses the natural abilities of bacteria and their plasmids to advance medical and biotechnological applications.