What is Plasmid DNA?
Essential genetic information is passed on to the next individual as part of the inheritance process during reproduction. Plasmid DNA is extrachromosomal DNA that is different from genomic DNA. It is circular in form and usually occurs inside bacterial cells. When compared to chromosomes, it is a smaller molecule with a variable number of copies in each cell. It has a replication origin, hence it is self-replicative by definition.
As a result, they are not reliant on genomic DNA and are capable of self-replication. This DNA codes for genes that produce results that aren't required for cell activity, such as nitrogen fixation, antibiotic resistance, and so on. As a result, genetic engineering can be used to introduce new genes.
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 is 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 making it easier to study and experiment.
What is Chromosomal DNA?
The genomic DNA found in prokaryotic and eukaryotic species is referred to as chromosomal DNA. Prokaryotic genomes have a single circular chromosome, whereas eukaryotic genomes have linear chromosomes. They are double-stranded and contain a replication origin; the occurrence of several replication origins in eukaryotes is due to their huge size. The number of chromosomes in a particular type varies from species to species.
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 unorganised 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
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 on their own terms.
FAQs on Difference Between Plasmid DNA and Chromosomal DNA
1. What is the main difference between plasmid DNA and chromosomal DNA?
The main difference lies in their function and necessity. Chromosomal DNA carries all the essential genetic information required for an organism's survival, growth, and reproduction. In contrast, plasmid DNA is extrachromosomal and contains non-essential genes that often provide special advantages, such as antibiotic resistance.
2. Where are plasmid and chromosomal DNA found inside a bacterial cell?
In a typical bacterial cell, the single, large chromosomal DNA molecule is found in a specific region of the cytoplasm called the nucleoid. The smaller plasmid DNA molecules are located separately, floating freely within the cell's cytoplasm.
3. How do chromosomal DNA and plasmid DNA differ in their structure and size?
Both are typically circular in bacteria, but they differ significantly in size. Chromosomal DNA is a very large, single molecule that contains millions of base pairs. Plasmid DNA molecules are extremely small in comparison, usually containing only a few thousand base pairs, and a cell can contain multiple copies of them.
4. Can a cell survive without chromosomal DNA? What about without plasmid DNA?
A cell absolutely cannot survive without its chromosomal DNA, as it contains the core instructions for all life processes. However, a cell can easily survive without plasmid DNA. The loss of a plasmid only means the loss of the specific traits it carried, not the loss of the organism's basic ability to live and reproduce.
5. Why is plasmid DNA often called 'extrachromosomal' DNA?
The term 'extrachromosomal' literally means 'outside the chromosome'. Plasmid DNA earns this name because it exists and replicates independently from the main chromosomal DNA within the cell. It is a separate genetic element not part of the primary genome.
6. If plasmids aren't essential for basic survival, why do bacteria have them?
While not essential for day-to-day life in a stable environment, plasmids provide a powerful survival advantage in challenging conditions. They often carry genes for:
- Antibiotic resistance
- Tolerance to heavy metals
- Production of toxins to compete with other microbes
7. What is the importance of plasmids in the field of biotechnology?
Plasmids are essential tools in genetic engineering and biotechnology. Because they are small, easy to handle, and self-replicating, scientists use them as vectors to carry foreign genes into bacteria. This allows for the mass production of important proteins, such as insulin, through a process called gene cloning.
