The key difference between 16s and 18s rRNA is that 16s rRNA is a component of the 30S subunit in prokaryotic ribosomes while 18s rRNA is a component of the 40S subunit in eukaryotic ribosomes.
Ribosomal RNA or rRNA is a structural component of ribosomes. rRNA is involved in the protein synthesis mechanism. Ribosomes of eukaryotes and prokaryotes vary. Eukaryotes have 80s ribosomes, while prokaryotes have 70s ribosomes. The rRNA composition also varies between the two ribosomes. While small subunits of eukaryotic ribosome contain 18s rRNA, small subunits of prokaryotic ribosome contain 16s rRNA.
CONTENTS
1. Overview and Key Difference
2. What is 16s rRNA
3. What is 18s rRNA
4. Similarities – 16s and 18s rRNA
5. 16s vs 18s rRNA in Tabular Form
6. Summary – 16s vs 18s rRNA
What is 16s rRNA?
16srRNA or 16s ribosomal RNA is a component of the 30s subunit of prokaryotic ribosome. Therefore, it is a part of the small subunit of the ribosome. The 16s rRNA plays an important role in stabilizing the translation mechanism along with the ribosome. The 16s rRNA binds to the shine Dalgarno sequence of the prokaryotic mRNA to initiate translation. It also binds with the 23s rRNA to assemble small and large subunits of the ribosome.
Figure 01: 16s rRNA
The 16s rRNA gene is present in the genome of all bacteria. It is a long, specific, and highly conserved region of the bacterial genome. Therefore, the detection of the 16s rRNA region in bacteria is an important step in the phylogenetic identification of bacteria. In this regard, universal primers can be designed to amplify the 16s rRNA region followed by sequencing.
What is 18s rRNA?
18s rRNA or 18s ribosomal RNA is a part of the eukaryotic ribosomal subunit 40s. Thus, it is a component of the small subunit of the eukaryotic ribosome. 18s rRNA associated with the ribosome plays an important role in the translation initiation in eukaryotes.
Figure 02: 18s rRNA
Gene coding for 18s rRNA is the 18s rRNA gene. The sequence from this gene is important in molecular analysis to reconstruct the evolutionary history of organisms as they are highly conserved regions. 18s rRNA has a high resolution for taxonomic studies in fungi where the internal transcribed spacer (ITS) region of 18s rRNA is mainly used for fungal diversity studies as a fungal barcode marker. The ITS region is mostly used in the metagenomic analysis.
What are the Similarities Between 16s and 18s rRNA?
- 16s and 18s rRNA are a part of the small subunit of the ribosome.
- Both 16s and 18s rRNA are found in the cytoplasm.
- Both have corresponding genes with a specific sequence.
- Moreover, both are important in translation initiation.
- They play an important role in phylogenetic analysis.
- Furthermore, they are important in predicting the evolution of species.
What is the Difference Between 16s and 18s rRNA?
16s RNA is found as a component in the 30s subunit of the prokaryotic ribosome. 18s rRNA is found as a component of the 40s subunit of the eukaryotic ribosome. Thus, this is the key difference between 16s and 18s rRNA. 16s rRNA is present in prokaryotes, while 18s rRNA is present in eukaryotes. Moreover, the gene that codes for 16s rRNA is important in bacterial species identification and taxonomy, while the 18s rRNA gene is important in fungal identification and classification.
The below infographic presents the differences between 16s and 18s rRNA in tabular form for side by side comparison.
Summary – 16s vs 18s rRNA
Ribosomal RNA or rRNA are structural components of the ribosome and form extensive secondary structures in recognizing conserved portions of mRNAs and tRNAs. 16srRNA is a component of the 30s subunit of prokaryotic ribosome. 18s rRNA is a part of the 40s subunit of the eukaryotic ribosome. So, this is the key difference between 16s and 18s rRNA. However, both form a part of the small subunit of the ribosome. Genes that code for both16s and 18s rRNA play an important role in the phylogenetic analysis of species as these genes are highly conserved.
Reference:
1. “18S Ribosomal RNA.” An Overview | ScienceDirect Topics.
2. “18S RRNA and Its Use in Fungal Diversity Analysis.” CD Genomics Blog.
Image Courtesy:
1. “16S r RNA svg” By !Original: Ikevin505Vector: Vezixig – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Structural organization of the 5′-terminal oart of the rDNA locus” By ST WE – Own work (CC BY-SA 3.0) via Commons Wikimedia