Linear DNA
Linear DNA is found in most eukaryotic cells. It has two open ends. The replication of linear DNA is a bit complex. It involves the formation of a replication fork which occurs in a bidirectional way. It continues till the final termination happens.
Circular DNA
Circular DNA is a form of closed-loop DNA that has no ends. This type of DNA is found in the cytoplasm of most prokaryotic cells. Also, it is seen in organelles like chloroplasts and mitochondria. The plasmid DNA is a classic example of extrachromosomal circular DNA. Here, the DNA is circular and has only one ori (origin of replication). Thus, replication is simple and happens in a unidirectional manner.
Both circular and linear DNA can be amplified by PCR techniques. Thus, they are used for research and diagnostic purposes.
Extended Reading: Difference between PCR, RT-PCR and qPCR
Difference between Linear and Circular DNA
| Linear DNA | Circular DNA |
|---|---|
| It is a linear structure that has two ends. | It is a circular structure with no ends. |
| Linear DNA is seen in the nucleus of eukaryotic organisms. | Circular DNA is seen in the cytoplasm of prokaryotic cells, organelles like chloroplast and mitochondria. |
| It is large in size. | It is comparatively smaller. |
| It has many origins of replication. Thus, replication is a bit complicated. | It has a single ori (origin of replication). Thus, replication is simple. |
Frequently Asked Questions on Difference between Linear and Circular DNA
What is extrachromosomal circular DNA?
This DNA is not found in the chromosomes. It is seen outside or inside the nucleus. The plasmid is a type of prokaryotic extrachromosomal DNA. In eukaryotes, some extrachromosomal DNA is observed in mitochondria. It is termed mtDNA (mitochondrial DNA). The inheritance of these DNA differs from the regular ones as they lack centromeres.
Can plasmids be linear?
The plasmids are usually circular structures. But linear confrontations can also be found. The linear plasmids need a specialised mechanism to replicate their ends.
What is DNA supercoiling?
It denotes the number of twists in a specific DNA strand. This supercoiling is vital for packaging the genetic material within the cell. When DNA is tightly twisted it is termed positive supercoiling. The twisting of DNA against the helical structure is called negative supercoiling.
Also Read: DNA Replication Process
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