The key difference between chromosomal DNA and extrachromosomal DNA is that chromosomal DNA is genomic DNA that is crucial in the development, growth and reproduction of an organism, while extrachromosomal DNA is non-genomic DNA that is found off the chromosomes and nonessential for the development, growth and reproduction of an organism.
The essential genetic information is passed on to the next generation during reproduction. This is part of the inheritance. A chromosome is a long DNA molecule that carries a part or whole genetic material of an organism. Living organisms can have both chromosomal and extrachromosomal DNA. Chromosomal DNA and extrachromosomal DNA comprises DNA, which is the basic unit of inheritance.
CONTENTS
1. Overview and Key Difference
2. What is Chromosomal DNA
3. What is Extrachromosomal DNA
4. Similarities Between Chromosomal DNA and Extrachromosomal DNA
5. Side by Side Comparison – Chromosomal DNA vs Extrachromosomal DNA in Tabular Form
6. Summary
What is Chromosomal DNA?
Chromosomal DNA is any DNA that is found in the chromosomes, either inside or outside of the nucleus of a cell. The most important function of DNA is to carry genes. It is the information that specifies all proteins of an organism. Chromosomal DNA is also called genomic DNA. Prokaryotes and eukaryotes have chromosomes. Therefore, they do have chromosomal DNA that is attached to proteins by strong interactions.
Prokaryotes do not possess nuclei. Hence, their chromosomal DNA is organized into a structure called the nucleoid. Prokaryotes carry a single circular chromosome comprised of double-stranded DNA. Moreover, prokaryotic chromosomal DNA is also attached to proteins and RNA molecules in the chromosome.
Figure 01: Chromosomal DNA
Eukaryotes have chromosomes that consist of a long linear chromosomal DNA molecule associated with proteins called histones. These chromosomal DNA and proteins form a compact complex called chromatin in eukaryotes. Eukaryotic chromosomal DNA is also double-stranded. Histones are responsible for making the most basic unit of chromosome organization, “the nucleosome”, with the help of chromosomal DNA. Furthermore, eukaryotes possess multiple, large, linear chromosomes in the nucleus of the cell that are made up of chromosomal DNA and proteins.
What is Extrachromosomal DNA?
Extrachromosomal DNA is any DNA that is found off the chromosomes, either inside or outside of the nucleus of a cell. Multiple forms of extrachromosomal DNA exist. Extrachromosomal DNA performs different biological functions. The plasmid is the extrachromosomal DNA found in prokaryotes such as bacteria. Consequently, plasmid DNA encodes very important genes, including metal resistance, nitrogen fixation, antibiotic resistance, etc. In eukaryotes, extrachromosomal DNA is primarily found in organelles such as mitochondrial DNA and chloroplast DNA. Extrachromosomal DNA is often used in research of replication as it is easy to identify and isolate.
Figure 02: Extrachromosomal DNA
Although extrachromosomal circular DNA is found in normal eukaryotic cells, it is a distinct feature that has been identified in the nucleus of cancer cells. The extrachromosomal DNA in cancer cells is due to gene amplification. This results in many copies of driver oncogenes and very aggressive cancers. Moreover, extrachromosomal DNA in the cytoplasm is structurally different from nuclear DNA. This is because cytoplasmic DNA is less methylated than nuclear DNA.
What are the Similarities Between Chromosomal DNA and Extrachromosomal DNA?
- They are made up of DNA.
- Both encode for genes.
- The function of both is important for cell integrity.
- They can be identified either inside or outside of the nucleus of a cell.
What is the Difference Between Chromosomal DNA and Extrachromosomal DNA?
Chromosomal DNA is any DNA that is found in chromosomes, either inside or outside of the nucleus of a cell. In contrast, extrachromosomal DNA is any DNA that is found off chromosomes, either inside or outside of the nucleus of a cell. So, this is the key difference between chromosomal DNA and extrachromosomal DNA. Moreover, chromosomal DNA is large in size, while extrachromosomal DNA is small in size.
The below infographic presents more differences between chromosomal DNA and extrachromosomal DNA in tabular form.
Summary – Chromosomal DNA vs Extrachromosomal DNA
DNA carries the genetic information of an organism. It is the basic unit of inheritance. DNA is found in or off chromosomes. Chromosomal DNA is any DNA that is found in the chromosomes, either inside or outside of the nucleus of a cell. On the other hand, extrachromosomal DNA is any DNA that is found off the chromosomes, either inside or outside of the nucleus of a cell. Thus, this is the summary of the difference between chromosomal DNA and extrachromosomal DNA.
Reference:
Trapitz, Peter, et al. “Structure and Function of y Chromosomal DNA.” Chromosoma, Springer-Verlag, Available here.
Chiu, Rossa W K, et al. “What Is Extrachromosomal Circular DNA and What Does It Do?” OUP Academic, Oxford University Press, 29 May 2020, Available here.
Image Courtesy:
1. “Y Chromosome DNA” By Archaeogenetics – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Map of the human mitochondrial genome” By Emmanuel Douzery – Own work (CC BY-SA 4.0) via Commons Wikimedia