Difference Between 16s rRNA and 16s rDNA

Key Difference – 16s rRNA vs 16s rDNA
 

Ribosomes are the biological sites of protein synthesis in all living organisms. Ribosomes contain two components; small subunit and a large subunit. Prokaryotic organisms and Eukaryotic organisms differ from the composition of ribosome they contain. Each subunit is composed of ribosomal RNA and different proteins. These two subunits fit together and work as one during the protein synthesis. Prokaryotic ribosomes are the 70S and they are composed of 30S small subunit and 50S large subunit. Eukaryotic ribosomes are 80S and they are composed of 40S small subunit and 60S large subunit. In prokaryotes, ribosomal RNA of the small subunit of ribosomes is known as 16s rRNA. This 16s rRNA is transcribed from the chromosomal DNA which is known as 16s rDNA. 16s rDNA is the gene which produces 16s rRNA by the transcription. The key difference between the 16s rRNA and 16s rDNA is that 16s rRNA is the transcribed single-stranded ribosomal RNA which is a component of the small subunit of prokaryotes while 16s rDNA is the double-stranded chromosomal DNA or the gene that code for 16s rRNA. Gene of the 16s rRNA is the 16s rDNA.

CONTENTS

1. Overview and Key Difference
2. What is 16s rRNA
3. What is 16s rDNA
4. Similarities Between 16s rRNA and 16s rDNA
5. Side by Side Comparison – 16s rRNA vs 16s rDNA in Tabular Form
6. Summary

What is 16s rRNA?

rRNA is a component of ribosomes. 16s rRNA is the specific component of 30S small subunit of the prokaryotic ribosome that binds with Shine-Dalgarno sequence. This 16s rRNA sequence shows high variability among the bacterial species. Hence, it can be used for the bacterial phylogeny and taxonomy.

What is 16s rDNA?

Prokaryotes have 70S ribosomes. The small subunit of the prokaryotic ribosomes is the 30S. The ribosomal RNA (rRNA) of the 30S small subunit is known as 16s rRNA, and the gene 16s rDNA codes it. Hence 16s  rDNA is known as 16s rRNA gene. 16s rDNA is chromosomal DNA. It is double-stranded, and it is a gene composed of coding and noncoding regions. When 16s rDNA gene is transcribed, it produces 16s rRNA sequence. 16s rDNA is universal DNA sequence in prokaryotes. However, the sequence of the 16s rDNA among the prokaryotes vary. It facilitates the use of 16s rDNA sequence in accurate identification of bacterial species and also for the discovery of novel bacterial species.

16s rDNA plays an important role in bacterial phylogeny and taxonomy. Therefore, it is used as a reliable molecular marker in phylogenetic studies of prokaryotes since it is highly conserved between different species. 16s rDNA nucleotide sequence has nine hypervariable regions (V1-V9) that provide a good source for differentiation of bacteria and archaea.

Figure 01: DNA and RNA

The sequencing of 16s rDNA gene has facilitated reclassification of the bacteria into new species or genera. Hence, this gene is used in molecular laboratories as a most common housekeeping marker for identification of microbes. There are several reasons that made 16srDNA as the best marker for identification of microbes such as the presence of 16srDNA in all bacteria, the unchanged nature of the function of the 16s rDNA gene over the time, and the large size of 16s rDNA that makes it enough for information purposes.

What are the Similarities Between 16s rRNA and 16s rDNA?

• Both are nucleic acids.
• Both are made up of nucleotides.
• Both are related to ribosomal RNA.

What is the Difference Between 16s rRNA and 16s rDNA?

Summary – 16s rRNA vs 16s rDNA 

16s rRNA is the ribosomal RNA component of the small subunit of ribosomes of prokaryotes. The gene 16s rDNA encodes this RNA sequence. 16s rRNA is single-stranded and 16s rDNA is double-stranded. This is the difference between 16s rRNA and 16s rDNA.

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Reference:

1.Janda, J. Michael, and Sharon L. Abbott. “16S rRNA Gene Sequencing for Bacterial Identification in the Diagnostic Laboratory: Pluses, Perils, and Pitfalls.” Journal of Clinical Microbiology, American Society for Microbiology, Sept. 2007. Available here  
2.“Ribosome.” Wikipedia, Wikimedia Foundation, 13 Jan. 2018. Available here  
3.Woo, P C, et al. “Then and now: use of 16S rDNA gene sequencing for bacterial identification and discovery of novel bacteria in clinical microbiology laboratories.” Clinical microbiology and infection: the official publication of the European Society of Clinical Microbiology and Infectious Diseases., U.S. National Library of Medicine, Oct. 2008. Available here 

Image Courtesy:

1.’Difference DNA RNA-EN’ By Sponk (talk) – chemical structures of nucleobases by Roland1952, (CC BY-SA 3.0) via Commons Wikimedia 

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