There are 5 shapes of plasmids: nicked open-circular, relaxed circular, linear, supercoiled, and supercoiled denatured. Plasmids vary in size from 1kb to several megabase pairs. Plasmids contain an origin of replication, antibiotic resistance genes, and other components like promoters. Plasmids are classified based on function into fertility, resistance, colicin, degradative, and virulence plasmids. They are also classified based on their ability to transfer into conjugative and non-conjugative plasmids. Plasmids can be isolated from bacterial cells through cell growth, centrifugation, lysis, protein and DNA separation, purification, precipitation, and storage

4. Shapes of plasmids
There are 5 shapes of plasmids;
Nicked Open-Circular: DNA has one strand cut.
Relaxed Circular: DNA is fully intact.
Linear: DNA has free ends.
Supercoiled: DNA is completely intact, but it has a twist to it
which makes it smaller.
Supercoiled Denatured: A little smaller in size than
supercoiled.

5. Size of Plasmid
Smaller plasmids are few in number and only a single
larger plasmid is present in each bacterium.
The size of the plasmid varies from several Kilo base pair
to several mega base pairs, depending on the type of
plasmid.
The size of the plasmid DNA is generally 1kb to 2 kb
the stability of the plasmid DNA is very high. It can
remain stable for a longer period of time as in a purified
state or in the bacterial cell.

6. Structure of plasmids

8. 1. Origin of replication (replicon)
2. Polylinker (multiple cloning sites) MCS
3. Antibiotic resistance gene
4. Some of the other components of plasmids include
promoter region transcriptional machinery.
Primer binding site: .
Selection Marker: The antibiotic resistance gene (ARG)

10. Types of Plasmids
Classification of Plasmids based on Function
1.Fertility Plasmids (F PLASMID)
2.Resistance Plasmids (R PLASMID)
3.Col Plasmids production colicines protien
4. Degradative Plasmids
5.Virulence Plasmids
6.Episome
an abacus-like plasmid or viral DNA that has the ability to incorporate itself in the DNA chromo
that hosts it

11. Classification of Plasmids based on
their
Ability To Transfer To Other Bacteria
Conjugative plasmids:
Non-conjugative plasmids
Intermediate classes of plasmids

12. Isolation of Plasmid
In order to get pure plasmid DNA for processes
as cloning and transfection and PCR
the process of plasmid Isolation must be carried out.

13. Cell development (growth of the bacterial cells)
Centrifugation
Suspension of the pellets in an isotonic solution -ethylene
diamine Tetraacetate
The cells are lysed by alkaline-sodium dodecyl sulfur to
degrade cell membrane
Precipitation of proteins -acidic potassium acetate
Centrifugation – sedimentation
Purification - A mixture of chloroform and phenol
Precipitate & clean – ethanol
Centrifuge to remove the plasmid DNA
store in TE ( Tris EDTA) solutions, dissolve, and keep in a
storage container