Main Difference – Prokaryotic vs Eukaryotic DNA
Prokaryotic and eukaryotic DNA carry genetic information for the development, functioning and reproduction of prokaryotes and eukaryotes respectively. Eukaryotes consist of membrane-bound nucleus whereas prokaryotes lack a membrane-bound nucleus. Prokaryotic DNA is double-stranded and circular. But, eukaryotic DNA is double-strand and linear. The amount of DNA in prokaryotic cells is much less than the amount of DNA in eukaryotic cells. Both prokaryotic and eukaryotic DNA undergo replication by the enzyme DNA polymerase. The main difference between prokaryotic and eukaryotic DNA is that prokaryotic DNA is found in the cytoplasm whereas eukaryotic DNA is packed into the nucleus of the cell.
This article studies,
1. What is Prokaryotic DNA
– Definition, Structure, Features
2. What is Eukaryotic DNA
– Definition, Structure, Features
3. What is the difference between Prokaryotic and Eukaryotic DNA
What is Prokaryotic DNA
The DNA which is carried by prokaryotes is called prokaryotic DNA. Prokaryotic DNA is found in the cytoplasm of bacteria. Some prokaryotic DNA is found as the circular plasmids, carrying additional information. That means prokaryotic DNA does not contain an enclosing nuclear membrane. Prokaryotic DNA is packed into a single circular chromosome. It resides in the region called nucleoid in the cytoplasm. Nucleoid-associated proteins are involved in the packaging of the prokaryotic chromosome in the nucleoid. They help prokaryotic DNA to form a looped structure.
The size of the prokaryotic DNA is around 160,000 to 12.2 million base pairs, depending on the species. Prokaryotic DNA contains a small number of genes. Functionally related genes are organized into operons. Since prokaryotic DNA is rich with genes, the amount of nonfunctional DNA is less. Prokaryotic DNA replication is relatively simple. Prokaryotic chromosome contains a single origin of replication where the initiation of DNA replication occurs. Therefore, a single replication folk and bubble is formed during the replication. The speed of the replication is relatively high in prokaryotes, 2000 nucleotides per second.
DNA polymerase is the enzyme involved in the DNA replication; this contains seven different enzyme families. Out of the seven DNA polymerase families, both prokaryotes and eukaryotes share three families of DNA polymerases: DNA polymerase A, B and Y. DNA polymerase C family is only contained by prokaryotes. Pol III is a replicative DNA polymerase, which belongs to the DNA polymerase family C.
Figure 1: Bacterial DNA
What is Eukaryotic DNA
The DNA which is contained by eukaryotes is called eukaryotic DNA. Eukaryotic DNA is found in the nucleus of eukaryotic cells. Some eukaryotic DNA is found in organelles like chloroplasts and mitochondria as well. Eukaryotic DNA is enclosed by a nuclear membrane. Eukaryotic DNA is organized into several linear chromosomes. Histones are the proteins, involved in the packaging of eukaryotic chromosomes inside the nucleus. Tight coiling and dense packing are the features of the packing of eukaryotic chromosomes.
Eukaryotes consist of a large number of base pairs in their chromosomes. Most of the eukaryotic DNA consist of several copies of the genome. The size of the human genome is around 2.9 billion base pairs, arranged into 23 homologous chromosome pairs. Eukaryotic genes are encoded for a single protein. Multiple proteins can be achieved by alternative splicing of exons during post transcriptional modifications. The gene density of eukaryotic DNA is low. Hence, the amount of nonfunctional DNA is high in eukaryotic DNA. Eukaryotic DNA replication occurs through multiple origins of replication. The speed of the replication is low in eukaryotes, 100 nucleotides per second.
Multiple protein subunits are involved in the DNA replication of eukaryotes. DNA polymerase families, X like Pol Pol β, Pol σ, Pol λ, Pol μ and terminal transferases and RT like telomerase are specially contained by eukaryotes.
Figure 2: Eukaryotic DNA
Difference Between Prokaryotic and Eukaryotic DNA
Location
Prokaryotic DNA: Prokaryotic DNA is found in the cytoplasm of prokaryotic cells as well as circular plasmids.
Eukaryotic DNA: Eukaryotic DNA is found in the nucleus of the cell, inside the chloroplast and mitochondria.
Organelle DNA
Prokaryotic DNA: Prokaryotic DNA is not found inside organelles.
Eukaryotic DNA: Some of the eukaryotic DNA is found inside chloroplast and mitochondria as well.
Size
Prokaryotic DNA: The size of the DNA is less than 0.1 pg in prokaryotes.
Eukaryotic DNA: The size of the DNA is high in eukaryotes, usually more than 1 pg.
GC/AT Content
Prokaryotic DNA: GC content is more than the AT content.
Eukaryotic DNA: AT content is more than 4xGC content.
Number of Copies
Prokaryotic DNA: Prokaryotic DNA consists of one copy of the genome.
Eukaryotic DNA: Eukaryotic DNA consists of more than one copies of the genome.
Number of Genes
Prokaryotic DNA: Prokaryotic DNA contains a small number of genes.
Eukaryotic DNA: Eukaryotic DNA contains a large number of genes.
Number of Chromosomes
Prokaryotic DNA: Prokaryotic DNA is organized into a single chromosome.
Eukaryotic DNA: Eukaryotic DNA is organized into many chromosomes.
Histones
Prokaryotic DNA: Prokaryotic DNA is not packed with histones.
Eukaryotic DNA: Eukaryotic DNA found in the nucleus packed with histones.
Circular/Linear
Prokaryotic DNA: Prokaryotic DNA is circular. Hence, they do not have ends.
Eukaryotic DNA: Eukaryotic DNA is linear, containing two ends.
Introns
Prokaryotic DNA: Introns are absent in prokaryotic DNA.
Eukaryotic DNA: Eukaryotic DNA consist of introns, interrupting the sequence of the coding region.
Nonfunctional DNA
Prokaryotic DNA: Prokaryotic DNA contains fewer amounts of nonfunctional DNA.
Eukaryotic DNA: Eukaryotic DNA contains higher amounts of nonfunctional DNA.
Transposons
Prokaryotic DNA: Prokaryotic DNA lacks transposons.
Eukaryotic DNA: Eukaryotic DNA consists of transposons.
DNA Replication
Prokaryotic DNA: Prokaryotic DNA replication occurs in the cytoplasm.
Eukaryotic DNA: Eukaryotic DNA replication occurs in the nucleus.
Origin of Replication
Prokaryotic DNA: Prokaryotic chromosome contains a single origin of replication.
Eukaryotic DNA: Eukaryotic chromosome contains many origins of replication.
Efficiency
Prokaryotic DNA: Prokaryotic DNA replication is rapid, 2000 nucleotides are added per second.
Eukaryotic DNA: Eukaryotic DNA replication is slow, 100 nucleotides are added per second.
Conclusion
Prokaryotic and eukaryotic DNA are the carriers of genetic information required for the development, functioning and reproduction of prokaryotes and eukaryotes. The main difference between prokaryotic and eukaryotic DNA is their quantity, information content, packing and replication. Prokaryotic DNA can be found in the cytoplasm whereas eukaryotic DNA is found in the nucleus, enclosed by the nuclear membrane. Prokaryotic DNA is organized into a single circular chromosome and eukaryotic DNA is organized into several linear chromosomes. The amount of eukaryotic DNA is higher than prokaryotic DNA. Several copies of the genome are found in the eukaryotic DNA as well. The replication of both prokaryotic and eukaryotic DNA occurs in the same way, but prokaryotic DNA replication is relatively simple. Both prokaryotes and eukaryotes contain DNA polymerases, which are capable of replicating and repairing the DNA. Eukaryotes contain telomerase and terminal transferases as well.
Reference:
1. Bank, E., Leaf Group. “List Ways in which Prokaryotic and Eukaryotic DNA Differ.” List Ways in which Prokaryotic and Eukaryotic DNA Differ | Education – Seattle PI. Seattle PI, 21 Jan. 2014. Web. 23 Apr. 2017.
Image Courtesy:
1. “Plasmid (english)” By User:Spaully on English wikipedia – Own work (CC BY-SA 2.5) via Commons Wikimedia
2. “Eukaryote DNA-en” By Eukaryote_DNA.svg (CC BY-SA 3.0) via Commons Wikimedia
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