Example:
Now how do you find these colonies on a flat plate? Plasmid? What do you want?
How do you know that there are colonies of plasmid we need on the plate now?
Plasmid is the genetic material outside the chromosome of bacteria, which exists in the cytoplasm and has the ability of self-replication, so that it keeps a constant copy number in the daughter cells and expresses the genetic information it carries. It is a closed-loop double-stranded DNA molecule.
Plasmids are not necessary for bacterial growth and reproduction, and can be eliminated by self-loss or manual treatment. The genetic information carried by plasmid can endow host bacteria with some biological characteristics, which is beneficial for bacteria to survive in specific environmental conditions.
Function of plasmid: It has the ability of self-replication, so that it keeps a constant copy number in daughter cells and expresses the genetic information it carries. Bacterial plasmid is a common vector in DNA recombination technology. Vector refers to a tool to deliver useful foreign genes into recipient cells for proliferation and expression through genetic engineering.
Recombination of a target gene fragment into plasmid constitutes a recombinant gene or recombinant. Then the recombinant is transformed into the recipient cell by microbial transformation technology, so that the target gene in the recombinant can be propagated or expressed in the recipient bacteria, thereby changing the original characteristics of the host cell or producing new substances.