RNA is a long, unbranched macromolecule (structure) made up of nucleotides connected by 3′ → 5′ phosphodiester bonds, present in viruses, prokaryotic cells, and eukaryotic cells, mainly found in the cytoplasm and serves for gene coding, decoding, regulation, and expression.
RNA plays a significant role as the main component of ribosomes. Its length can vary, containing anywhere from 75 to several thousand ribonucleotides.
The discovery of RNA’s role in regulating gene expression through RNA interference (RNAi) has prompted scientists to reevaluate the importance of RNA.
The term “RNA world” was first introduced by Nobel laureate Walter Gilbert in 1986.
The RNA World hypothesis suggests that self-replicating RNA molecules were the ancestors of all current life on Earth, with RNA initially serving as the genetic material before DNA evolved later.
Features of RNA
- RNA is synthesized in the nucleolus and then moves to specific regions in the cytoplasm depending on its type.
- It Contain ribose sugar, RNA is more chemically reactive than DNA and unstable in alkaline conditions. Its larger helical grooves make it more susceptible to enzymatic attacks.
- RNA strands are constantly synthesized, degraded, and recycled, and they are more resistant to UV damage compared to DNA.
- RNA has a relatively higher mutation rate, and unusual bases may be present.
- The amount of RNA can vary between different cells.
- After melting, RNA renatures quickly.
- RNA is more versatile than DNA, able to perform a wide range of tasks in an organism.
- It is a polymer molecule essential for various biological functions, including gene coding, decoding, regulation, and expression.
Structure of RNA
- RNA is a polymer composed of individual ribonucleotides.
- Each ribonucleotide consists of three components: a phosphate group, a five-carbon ribose sugar, and a nitrogenous base.
- Adenine, guanine, and cytosine are present in both DNA and RNA, while thymine is unique to DNA and uracil is specific to RNA.
- The phosphate group is linked to the ribose sugar by a phosphodiester bond, and the sugar is connected to a nitrogenous base.
- The nitrogenous bases are classified as either purines or pyrimidines.
- Purines, which have two fused rings, include adenine and guanine.
- Pyrimidines, which have a single ring, include cytosine and uracil.
- RNA has 4 types of nucleosides, they are ribose adenosine, ribose guanosine, ribose cytidine and ribose Uridine
- Bases are abbreviated as A, C, G, and U, and these letters are also used to represent the entire nucleotide within RNA polymers.
- Nucleotides of RNA are Called Ribonucleotides. RNA has four types of nucleotides, they are ribose adenylic acid (ribose adenosine monophosphate), ribose guanylic acid (ribose guanosine monophosphate), ribose cytidylic acid (ribose cytidine monophosphate) and ribose uridylic acid (ribose uridine monophosphate).
- In nucleotides, the 1′ carbon of the ribose is bonded to nitrogen at position 9 in purines or position 1 in pyrimidines.
- The phosphate group imparts acidic properties to nucleotides, typically releasing a hydrogen ion (H+) and leaving the phosphate negatively charged under typical cellular conditions.
- RNA base pairing differs slightly from DNA. In RNA, if base pairing present, cytosine pairs with guanine, adenine pairs with uracil, and guanine can also pair with uracil. Other interactions, such as guanine-adenine pairing in the GNRA tetraloop, can also occur.
General functions of RNA
- RNA serves as a messenger between DNA and ribosomes.
- In certain organisms, like viruses, RNA functions as the genetic material.
- Some RNA molecules are directly involved in biological processes by catalyzing reactions, regulating gene expression, or detecting and relaying cellular signals.
- Messenger RNA (mRNA) carries genetic information from DNA in the nucleus to ribosomes in the cytoplasm.
- Ribosomal RNA (rRNA) is a key component of ribosomes, where it reads and decodes mRNA.
- Transfer RNA (tRNA) transports amino acids to the ribosome, where they are assembled into proteins.
- Certain RNA molecules, called ribozymes, can catalyze chemical reactions, such as splicing RNA or facilitating peptide bond formation in the ribosome.
