The document discusses properties of plasmids, which are self-replicating DNA elements found in prokaryotic and some eukaryotic cells. Key points include: - Plasmids are usually circular DNA molecules that can replicate independently of the host cell's chromosome. - They carry genes that allow for their own replication and can also carry genes that affect host cell properties. - Plasmids can exist in varying copy numbers within a host cell and some are capable of transferring between bacterial cells. - Common plasmid functions include antibiotic resistance, virulence factors for pathogenicity, and mediating tumor formation in plants by Agrobacterium.

1. Dr. S. V. Bakiya Laksmi.,
Assistant Professor of Biotechnology,
Bon Secours college Thanjavur.
M.Swetha , Msc.Biotechnology.
Plasmids

2. Plasmids:
• Self-replicating genetic elements that are sometimes
found in both prokaryotic and eukaryotic cells.
• Double Stranded DNA although rare linear plasmids and
RNA plasmids are known.
• They are not chromosomes nor part of the host cells and
permanent genome.

3. Properties of plasmids:
• Plasmids are usually circular molecules of DNA, although occasionally, plasmids
that are linear or made of RNA exist.
• Plasmids can only multiply inside a host cell. Most plasmids inhabit bacteria, and
indeed around 50% of bacteria found in the wild contain one or more plasmids.
• Most plasmids are circular, made of DNA, and much smaller than chromosome.
• Some plasmids are present in one or two copies per cell, whereas others occur in
multiple copies.
• Plasmids carry genes for managing their own lifecycles and some plasmids carry
genes that affect the properties of the host cell.

4. Plasmids as Replicons

5. • Cryptic plasmids are those that confer no identifiable phenotype on the host
cell.Cryptic plas-mids presumably carry genes whose characteristics are still
unknown.
• Certain plasmids can move themselves from one bacterial cell to another, a prop-
erty known as transferability.
• Many small plasmids, including the ColE plasmids have mobilizability, meaning
they can be mobilized by self-transferable plasmids (i.e., they are Mob
[mobilization-positive])
1. Copy number:
The number of copies of a plasmid found within a single host celcryptic
plasmid A plasmid that confers no identified characteristics or phenotypic
properties
1. Mobilizity: Ability of a non-transferable plasmid to be moved from one host cell
to another by a transferable plasma.
2. Transferability:Ability of a plasmid to move itself from one host cell to another

6. PLASMIDS REPLICATE IN STEP WITH THE HOST
CELL:

7. Plasmids compatible and incompatibility:

8. Bidirectional plasmid Replication:

9. Two types of replicate methods:
• Typical plasmid of circular double-stranded DNA use two alternative
mechanisms for replicating their DNA.
• They have an original of Replication where the DNA opens and
and replication begins.
• They two replication forks move around the circular plasmids DNA in
Opposite direction until they meet.
Rolling circle Replication
Bidirectional plasmids Replication

10. Rolling circle Replication:

12. Properties by naturally occurring plasmids

13. Antibiotic Resistance plasmids

14. ColE1 Plasmid:

15. Priming of colE1 plasmid:

16. Antisense RNA prevents primer formation:

17. Virulence plasmids:
• Virulenceplasmids help bacteria infect humans.animals,or even plants
by a variety of mechanisms.
• Some virulence factor are toxins that damage or kill animal cells
others help bacteria to attach to and invade animal cells.
• A variety of toxins are found in different pathogenic E.coli strains,
• Eg: Heat liable Enterotoxin. Choleratoxinn
. Heat stable Enterotoxin Hemolysin

18. Toxin and adhesins:

19. Ti Plasmids:

20. Formation of tumor by Agrobacterium:

21. Crown gall tumor by Agrobacterium:

22. Plasmid of yeast:

23. Plasmid of yeast:

24. Plasmids as virus:

25. Inactivation of penicillin By lactomase

26. Inactivation of lactomase by clavulanic acid:

27. Inactivation of aminoglycoside antibiotics

28. Idea of Gene creature: