Difference Between Genomic DNA and Plasmid DNA Isolation

The key difference between genomic DNA and plasmid DNA isolation is that the genomic DNA isolation targets the extraction of genomic DNA while the plasmid DNA isolation targets the extraction of plasmid DNA of the bacteria.

DNA isolation is a chemical process that used to isolate DNA from different species or from different samples. DNA isolation is important in downstream molecular biology techniques, such as gel electrophoresis, polymerase chain reaction and DNA sequencing techniques. Therefore, isolation of DNA is an essential chemical process in molecular biological studies. Based on the purpose of the research, sometimes it is necessary to isolate genomic DNA. In addition, some studies focus on isolating plasmid DNA from bacteria. Genomic DNA isolation is the process of isolating genomic DNA from a prokaryotic or a eukaryotic sample. The steps of isolation differ according to the type of the cell in which the DNA is isolating. Plasmid DNA isolation is the process of isolating plasmid DNA from a bacterial cell. In comparison to genomic DNA isolation, the overall process is complex in plasmid DNA isolation.

CONTENTS

1. Overview and Key Difference
2. What is Genomic DNA Isolation
3. What is Plasmid DNA Isolation
4. Similarities Between Genomic DNA and Plasmid DNA Isolation
5. Side by Side Comparison – Genomic DNA vs Plasmid DNA Isolation in Tabular Form
6. Summary

What is Genomic DNA Isolation?

Genomic DNA isolation is the process of extracting whole genomic DNA of an organism. This particular process involves three main events. They are, cell lysis or nuclear lysis, protein degradation or proteolysis and precipitation of genomic DNA. The lysis step may differ according to the cell type. In prokaryotes, since there is a peptidoglycan cell wall, the first step should be the breakdown of the cell wall. On the other hand, in eukaryotes, the lysis step involves the breakdown of the plasma membrane and the nuclear membrane to take out the DNA to the exterior. In contrast, special steps are essential to lyse the plant and fungal cell walls.

Consequently, once the lysis step completes, eventually DNA will come to the supernatant. Simultaneously, protein degradation also takes place in the solution due to the addition of proteinase K. Next step is to separate genomic DNA and degraded proteins from each other. Hence, the degraded proteins separate out by precipitation allowing the genomic DNA to remain in the supernatant. After precipitation of proteins, genomic DNA can be precipitated and re-suspended in a suitable buffer until it requires for the experiment.

Genomic DNA, which is linear DNA contains all the genetic information of an organism. In other words, the genome is the heredity material of a living organism which is responsible for all the structural and functional activities of the cell. It consists of both coding and non-coding DNA sequences. When isolating genomic DNA, it includes the entire genome of the organism.

What is Plasmid DNA Isolation?

Plasmid DNA isolation is a special and more complicated process of DNA isolation. Plasmids are extrachromosomal DNA present in most bacterial cells. They are dormant circular DNA which supports the bacteria to survive in harsh environmental conditions. Plasmid DNA consists of special resistant genes that provide additional advantages to the bacteria such as antibiotic resistance, virulence properties and toxic properties.

Plasmid DNA isolation also involves three main processes; cell lysis, proteinolysis and DNA precipitation. Although the biochemical mechanism of isolation is similar to that of the genomic DNA isolation, the process is more complex than it. The cell lysis process is the most important process in this procedure. Most importantly, genomic DNA and plasmid DNA should not be mixed with each other. Therefore, a much milder lysis process incorporates into the plasmid DNA isolation procedure. Hence, in most plasmid DNA isolation procedures use the detergent; sodium dodecyl sulfate for the cell lysis.

What are the Similarities Between Genomic DNA and Plasmid DNA Isolation?

• Genomic DNA and Plasmid DNA isolation focus on extracting DNA of an organism.
• Also, both follow the same overall process which includes cell lysis, protein degradation and DNA precipitation.
• Furthermore, resulting DNA of both processes are important for downstream processes.
• Moreover, both isolation processes include the steps to purify and store the DNA under specified storage conditions.
• Besides, proteinase K is used in both methods to degrade proteins.

What is the Difference Between Genomic DNA and Plasmid DNA Isolation?

Genomic DNA isolation focuses on extracting entire genomic DNA of the target organism while the plasmid DNA isolation focuses on isolating only plasmid DNA from the particular bacterial species. Therefore, this is the key difference between genomic DNA and plasmid DNA isolation. Moreover, another difference between genomic DNA and plasmid DNA isolation is in the procedure. The genomic DNA isolation is a less complex procedure compared to plasmid DNA isolation. Hence, when isolating plasmid DNA, it is necessary to take precautions to prevent the mixing of genomic and plasmid DNA with each other.

The below infograohic provides further details on the difference between genomic DNA and plasmid DNA isolation.

Summary – Genomic DNA vs Plasmid DNA Isolation

DNA isolation is an important process in molecular biology techniques. There are two types of DNA namely genomic DNA and plasmid DNA (extra-chromosomal DNA). Based on the requirement, some procedures carried out to isolate genomic DNA while some procedures focus of isolating only plasmid DNA from bacteria. Hence, the steps involved in both processes differ slightly from each other. However, the overall process is the same in both isolations. Isolated DNA of both processes has immense use in downstream processes such as cloning, gel electrophoresis and polymerase chain reactions. At the end of the genomic DNA isolation protocol, the entire genomic DNA of the organism can be isolated as the final product while at the end of the plasmid DNA isolation protocol, the plasmid DNA of the respective bacterium can be isolated as the final product. Therefore, this is the difference between genomic DNA and plasmid DNA isolation.

Reference:

1.“DNA EXTRACTION FROM BACTERIA.” DNA Extraction from Bacteria. Available here 

Image Courtesy:

1.”DNA Extraction”By Joo Nath – Own work, (CC BY-SA 4.0) via Commons Wikimedia 
2.”Plasmid miniprep”By Retama – Own work, (CC BY-SA 4.0) via Commons Wikimedia