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18S ribosomal RNA
{{Short description|Overview of 18S ribosomal RNA in eukaryotes}}


[[File:Eucaryot_rdna.png|thumb|Diagram of eukaryotic ribosomal DNA, including 18S rRNA.]]
==18S Ribosomal RNA==
[[File:Eucaryot rdna.png|thumb|right|Diagram of eukaryotic rDNA, including 18S rRNA]]
The '''18S ribosomal RNA''' (18S rRNA) is a component of the small [[ribosomal subunit]] in [[eukaryotes]]. It is a part of the [[ribosome]], which is essential for [[protein synthesis]] in all living cells. The 18S rRNA is homologous to the 16S rRNA found in [[prokaryotes]].


The '''18S ribosomal RNA''' (18S rRNA) is a component of the small [[ribosomal subunit]] in [[eukaryotic]] organisms. It is a part of the [[ribosome]], which is essential for [[protein synthesis]] in cells. The 18S rRNA is homologous to the 16S rRNA found in [[prokaryotes]].
==Structure and Function==
The 18S rRNA is a single-stranded RNA molecule that folds into a complex three-dimensional structure. This structure is crucial for its role in the [[ribosome]], where it helps to maintain the correct alignment of the [[mRNA]] and the [[tRNA]]s during [[translation (biology)|translation]]. The 18S rRNA also plays a role in the catalytic activity of the ribosome, facilitating the formation of [[peptide bonds]].


==Structure==
==Genomic Organization==
The 18S rRNA is a single-stranded RNA molecule that folds into a complex secondary structure. It is approximately 1,800 nucleotides long and forms part of the 40S subunit of the eukaryotic ribosome. The structure of 18S rRNA includes several conserved regions that are crucial for its function in the ribosome.
In eukaryotes, the 18S rRNA gene is part of the [[ribosomal DNA]] (rDNA) repeat unit, which also includes the 5.8S and 28S rRNA genes. These rDNA repeats are typically found in the [[nucleolus]] of the cell, where they are transcribed by [[RNA polymerase I]].


==Function==
==Evolutionary Significance==
The primary function of 18S rRNA is to contribute to the formation of the [[ribosome]] and to facilitate the accurate translation of [[mRNA]] into [[proteins]]. It plays a critical role in the binding of the mRNA and the [[transfer RNA]] (tRNA) during the translation process. The 18S rRNA also helps maintain the correct alignment of the ribosomal subunits and the mRNA.
The 18S rRNA is highly conserved across eukaryotic species, making it a valuable tool for [[phylogenetic]] studies. It is often used in [[molecular phylogenetics]] to infer evolutionary relationships among organisms. The sequence variations in 18S rRNA can provide insights into the evolutionary history and [[taxonomy]] of eukaryotes.
 
==Role in Phylogenetics==
18S rRNA is widely used in [[phylogenetic]] studies to determine evolutionary relationships among eukaryotic organisms. Due to its highly conserved nature, it serves as a molecular marker for identifying and classifying species. The sequence variations in 18S rRNA can provide insights into the evolutionary history and divergence of different species.


==Applications in Research==
==Applications in Research==
In addition to its role in phylogenetics, 18S rRNA is used in various research applications, including:
[[File:18S ribosomal RNA.png|thumb|left|Secondary structure of 18S rRNA]]
* '''Environmental microbiology''': It is used to study microbial communities in different environments by analyzing the 18S rRNA gene sequences.
The 18S rRNA gene is commonly used as a [[molecular marker]] in [[environmental microbiology]] and [[metagenomics]] to identify and classify eukaryotic microorganisms in various environments. It is also used in [[clinical diagnostics]] to detect and identify pathogenic eukaryotes.
* '''Medical diagnostics''': 18S rRNA sequences can be used to detect and identify pathogenic eukaryotic microorganisms in clinical samples.
* '''Biotechnology''': It is used in the development of genetically engineered organisms and in the study of gene expression.


==Related pages==
==Related pages==
* [[Ribosomal RNA]]
* [[Ribosomal RNA]]
* [[Ribosome]]
* [[Ribosome]]
* [[Protein synthesis]]
* [[Translation (biology)]]
* [[Phylogenetics]]
* [[Phylogenetics]]
* [[Molecular biology]]


[[Category:Molecular biology]]
[[Category:Molecular biology]]
[[Category:Ribosomal RNA]]
[[Category:RNA]]
[[Category:RNA]]
[[Category:Ribosomal RNA]]

Revision as of 12:09, 15 February 2025

Overview of 18S ribosomal RNA in eukaryotes


18S Ribosomal RNA

Diagram of eukaryotic rDNA, including 18S rRNA

The 18S ribosomal RNA (18S rRNA) is a component of the small ribosomal subunit in eukaryotes. It is a part of the ribosome, which is essential for protein synthesis in all living cells. The 18S rRNA is homologous to the 16S rRNA found in prokaryotes.

Structure and Function

The 18S rRNA is a single-stranded RNA molecule that folds into a complex three-dimensional structure. This structure is crucial for its role in the ribosome, where it helps to maintain the correct alignment of the mRNA and the tRNAs during translation. The 18S rRNA also plays a role in the catalytic activity of the ribosome, facilitating the formation of peptide bonds.

Genomic Organization

In eukaryotes, the 18S rRNA gene is part of the ribosomal DNA (rDNA) repeat unit, which also includes the 5.8S and 28S rRNA genes. These rDNA repeats are typically found in the nucleolus of the cell, where they are transcribed by RNA polymerase I.

Evolutionary Significance

The 18S rRNA is highly conserved across eukaryotic species, making it a valuable tool for phylogenetic studies. It is often used in molecular phylogenetics to infer evolutionary relationships among organisms. The sequence variations in 18S rRNA can provide insights into the evolutionary history and taxonomy of eukaryotes.

Applications in Research

File:18S ribosomal RNA.png
Secondary structure of 18S rRNA

The 18S rRNA gene is commonly used as a molecular marker in environmental microbiology and metagenomics to identify and classify eukaryotic microorganisms in various environments. It is also used in clinical diagnostics to detect and identify pathogenic eukaryotes.

Related pages