What is Plasmid DNA?
- A plasmid DNA is a small circular piece of DNA that can independently replicate without the host’s chromosomal DNA.
- It is found in bacteria and exists naturally in eukaryotes like plants and yeast and can also be found in archaea.
- Some of the functional benefits of plasmid DNA to its host include degradative functions, resistance to antibiotics and virulence.
- Natural plasmid DNA has an origin of replication and a gene such as an antibiotic resistance gene. On the other hand, artificial plasmid DNA used in laboratories are designed to introduce foreign DNA into another cell. The latter kind of plasmid DNA consists of an origin of replication, cloning site and selection marker.
- Scientists or bioengineers find plasmid DNA as a great tool as it is easily modifiable and has the ability to self-replicate within a cell that makes it easier to study and experiment.
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What is Chromosomal DNA?
- Chromosomal DNA is a DNA molecule having all of the genetic information in the genome of an organism.
- Most of the eukaryotic chromosomal DNA consists of packaging proteins and chaperone proteins which bind to the DNA molecule and condense it to prevent tangling and becoming an unorganized structure.
- An important function of chromosomal DNA is to carry genetic information which is the functional unit of heredity. As we know, a gene is a segment of DNA that consists of instructions to make a particular protein or related proteins, and this gene is carried by the chromosomes. Chromosomes contain many genes and are present within the cell nucleus and mitochondria.
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Chromosomal DNA vs Plasmid DNA
|Characteristics/Features||Plasmid DNA||Chromosomal DNA|
|It is always double stranded.||It is single-stranded or double-stranded.|
|Shape||It is circular in shape.||It may be linear or circular in shape.|
|Histone proteins||Plasmid DNA is naked without the presence of histone proteins.||It is coated with histone proteins.|
|Presence||Plasmids are separated from bacterial genomic DNA.||Chromosomal DNA freely floats in the cytoplasm of bacterial cells while in eukaryotic organisms, they are found inside the nucleus.|
|Vital genes||It doesn’t carry any vital gene which is necessary for the cells. However, plasmids contain genes which provide benefits to bacteria including antibiotic/herbicide/pesticide resistance, drought tolerance, etc.||It carries multiple genes which are vital for cells to carry genetic information and hereditary properties. These are important for the well being and survival of organisms.|
|Self-replication||It has self-replicating properties without the main genome help.||It replicates with the genome only.|
|Genetic factor||It doesn’t act as a genetic factor and is often termed as extrachromosomal DNA.||Chromosomal DNA acts as a genetic factor.|
|Introns/Exons||Introns are absent in plasmid DNA, only exons are present.||It comprises both introns and exons.|
|Size||It is smaller than chromosomal DNA.||It is larger in size as compared to the plasmid DNA.|
|Quantity||Their number in a cell varied from 1-1000.||Their number varies depending upon species.|
|Transfer||It is transferred by horizontal gene transfer.||It is transferred by cell division.|
|Rate of Replication||It has a higher rate of replication.||It has a comparatively lower rate of replication.|
In the above tabular chart, we discussed the difference between plasmid and chromosomal DNA, now we shall see the existing similarities between the two.
Similarities Between Plasmid and Chromosomal DNA
- Both plasmid DNA and chromosomal DNA are present in bacterial cells.
- Both chromosomal DNA and plasmid DNA contain genes and are composed of DeoxyriboNucleic Acid (DNA).
- Both are highly significant in their own terms.
FAQ (Frequently Asked Questions)
- Distinguish Between Plasmid DNA and Chromosomal DNA.
Ans. Plasmid DNA and chromosomal DNA, both, contain genetic material, however many differences exist between the two. The former kind is present only in bacterial cells whereas the other is present in bacterial cells as well as eukaryotic cells. Plasmid DNA is called extrachromosomal DNA and its genetic material is not too vital for hereditary purpose, whereas the latter has a great importance in carrying genetic information from one generation to another. Plasmid DNA is used as vectors in biotechnological studies and has importance in molecular biology. It also provides resistance from pesticides, insecticides and herbicides to the bacterial cells. Plasmid DNA are self replicative whereas the chromosomal DNA uses the genome for replication.
- What are the Shapes of Plasmid DNA and Chromosomal DNA?
Ans. Plasmid DNA is linear in shape whereas chromosomal DNA can be linear or circular in shape. Naturally, plasmid DNA is present as a tightly supercoiled circle to allow itself to fit inside the cell. Chromosomal DNA is often observed as X-shaped structures.