Existing independent of the genome, both plasmids and episomes are types of DNA elements.
The differentiating factor between plasmid and episome is that plasmids do not integrate into the genome, while the episome can integrate into the genome. In addition, primarily, plasmids can be seen in prokaryotes whereas, in the eukaryotes, the episomes serve as plasmids in the prokaryotes.
Plasmid
- Plasmids are often circular, small molecules of DNA seen in bacteria and other cells
- It separates from the chromosome of the bacteria and independently replicates
- They are significant for the evolution of bacteria and for adaptation to the changing surroundings as it carries the genes with beneficial attributes for the cells of the bacteria
- Its size varies in the range of 1 to 200 kb
- It benefits the host by participating in the production of enzymes that degrades antibiotics
- It can be single or multiple copies and carry several tens to a hundred genes
- These can multiply in the cell of the host only
Episome
- These are segments of DNA in some cells, particularly the bacterial cells, which can exist either as a portion of a chromosome or autonomously in the cytoplasm
- Some of the episomes are viruses, transposons and insertion sequences
- In eukaryotes, the episomes are extrachromosomal, closed circular molecules of DNA of a viral genome origin or plasmids
- When it is integrated, a new copy of the episome is produced in the host chromosome which experiences replication
- The viral genetic content, as an autonomic unit, destructs the host cell as it uses the machinery of cellular replication for the production of new copies of self
- However, when it is integrated into the chromosome of the bacteria, it multiplies when the cell divides and is passed to the daughter cells. F factor is a type of episome
Key Difference between Plasmid and Episome
The table below depicts the difference between Plasmid and Episome.
|
Plasmid |
Episome |
|
What is it? |
|
|
These are circular, small DNA molecules (double-stranded extrachromosomal) of bacteria |
Larger than plasmids, these are a type of extrachromosomal DNA |
|
Occurs in prokaryotes or eukaryotes? |
|
|
Prokaryotes |
Both in eukaryotes as well as prokaryotes |
|
Size |
|
|
Usually small |
Larger |
|
Can it associate with chromosomal DNA? |
|
|
No, fails to associate with bacterial chromosomal DNA |
Integrates with chromosomal DNA. |
|
Can it be deployed as a vector? |
|
|
Yes, it carries a foreign fragment of DNA when introduced into it. |
Primarily, not used as a vector |
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