RNA : Defination, Types, Structure and functions

In general, RNA (Ribonucleic Acid) is a series of nucleotides that are bound together like chains. RNA is the result of transcription of a DNA fragment, so RNA as a polymer is much shorter when compared to DNA

In contrast to DNA which is commonly found in cell nuclei, most of the RNA is present in the cytoplasm, especially in the ribosome. RNA functions As a store of information As an intermediary between DNA and protein in the process of genetic expression because it applies to living organisms. RNA plays an equally important role in the body of any living creature, as does DNA. RNA works by mimicking the genes of DNA in the body. In addition, it is also helpful in transporting other genetic material to the cells.

RNA : Defination, Types, Structure and functions


History of RNA
RNA was discovered by Severo Okoa, Robert Hawley and Carl Vosse. The important functions of RNA are to smooth genes and produce copies of them. It also serves to connect different types of proteins. There are several varieties, among which ribosomal RNA, transfer RNA and messenger RNA are the main ones. The chain of RNA consists of groups of phosphates and ribose, to which its four basic elements, adenine, cytosine, guanine, and uracil, are attached. Unlike DNA, RNA is a single chain, with the help of which it encapsulates itself in the narrow shape of the cell.

RNA structure
The full name of RNA is Ribose Nucleic Acid. It is made up of single polyribonucleotide chain. It contains Ribonucleoside and Ribonucleotide
RNA mainly constist of
• D-Ribose sugar
• Phosphate
• Nitrogen base

RNA consists of a chain of polybonucleotides whose bases are usually adagine, guanine, uracil and cytosine. RNA is in the nucleus or cytoplasm of cells. Shaped from more RNA than DNA, RNA has a molecular weight of 25,000 to several million. Generally RNA contains a single polynucleotide chain, but the usual chain is folded to form a double helix region containing base pairs A: U and G: C.

RNA molecules have different forms from DNA, RNA has a single band shape and is not selected. Each RNA band is a polynucleotide composed of many ribonucleotides. Each ribonucleotide is composed of ribose sugar, nitrogenous bases and phosphoric acid. The base of nitrogen RNA is divided into two namely purine base and pyrimidine base. Purine bases are the same as DNA made up of adenine (A) and guanine (G), whereas pyrimidine bases are different from DNA, which are composed of cytosine (C) and uracil (U).

The RNA stage bone is composed of ribose and phosphate sequences, Ribonuleotide RNA is freely present in nucleoplasms in the form of nucleoside triphosphates such as adenosine triphosphate (ATP), guanosine triphosphate (GTP), cystidine triphosphate (CTP) and Uridin triphosphate (UTP). RNA is synthesized by DNA in the cell nucleus by using DNA as a template.


Functions of RNA 

The different types of RNA are involved in a various cellular process. The Main functions of RNA is :

  1. It Initiats the translation of DNA into proteins by the process of central Dogma.
  2. RNA Functions as an adapter molecule in  protein synthesis.
  3. RNA functions As a store of information As an intermediary between DNA and protein in the process of genetic expression because it applies to living organisms.  
  4. RNA works by mimicking the genes of DNA in the body. In addition, it is also helpful in transporting other genetic material to the cells.
  5. m-RNA Serves as a messenger between the DNA and the ribosomes.
  6. They Promotes the ribosomes to choose the right amino acid which is required in building up of new proteins in the body.
  7. RNA plays an equally important role in the body of any living creature, as does DNA.
  8. They are the carrier of genetic information in all living cells.


Types Of RNA

Mainly There are three types of RNA:

1. mRNA or messenger RNA:
mRNA or messenger RNA receive information from the DNA located in the nucleus for protein synthesis to the location of protein synthesis. mRNA is produced using the strand of DNA as a template. Due to which mRNA has complementary bases. T-RNA comprises 3–5% of the total RNA in a cell.

In prokaryotic cells more than one polypeptide chain is formed from the same mRNA. Therefore, these mRNAs are called polycistronic RNA. Whereas eukaryotic cells contain information for the synthesis of only one polypeptide chain from one mRNA. Which is called monocistronic RNA.


2. tRNA or transfer RNA:
It is the shortest RNA. In which 75–95 ribonucleotides are found. It transfers amino acids to the A-site of the ribosome at the time of protein synthesis. There are specific tRNAs for each 20 amino acids. Each tRNA is specific to the same amino acid. And carries amino acids from the cytoplasm to the ribosome for protein synthesis. Therefore, tRNA or transfer RNA in a cell is also known as Soluble RNA or Adaptor RNA. 16-18% of total RNA in a cell is t-RNA. Robert Hawley presented the tover Clover Leaf structure according to which tRNA has four arms -

Acceptor arm:
This arm has 5 'and 3' ends. CCA (cytosine-cytosine adenine) are alkali at the 3 'end and G (guanine) at the 5' end. The amino acid has a carboxyl group (-COOH). Connects via CCA's adenosine at the 3 'end.

Anticodon Arm:
This arm is the opposite arm of the receptive arm. It has a special sequence of three bases. Which is called Pratikodon. These replicons are the prototypes of codons located on mRNA. For example, if mRNA contains AUG codons then tRNA will be UAG codon.

TψC arm:
This arm helps to link tRNA to the ribosome.

DHU arm (DHU arm):
This arm helps to attach to the enzyme. This DHU's full name is dihydrouridine, which is an uncommon alkali.

tRNA contains some unusual bases such as Inosine and Dihydrouridine etc.


3. rRNA or ribosomal RNA:
rRNA is a component of ribosomes. It forms 80% of the ribosome. Ribosomes consist of ribonucleo proteins and rRNA. Synthesis of rRNA results from information contained in ribosomal genes found in the nucleolar organisor region of the chromosome. 80% of the total RNA found in a cell is rRNA.
  1. The 70s type of ribosome is found in prokaryotic cells, mitochondria, and lobes. Which consists of two sub-units 50s and 30s.
  2. The 50s ribosome contains 23s rRNA, 5s rRNA. Whereas 30s ribosome contains 16s rRNA.
  3. 23s rRNA contains about 3000 ribonucleotides, 5s rRNA contains about 120 ribonucleotides, 16s rRNA 1500 ribonucleotides.
  4. The 80s type of ribosome is found in the eukaryotic cell. Which consists of two sub-units 60s and 40s.
  5. The 60s ribosome contains 28s, 5.8s and 5s rRNA. While 40s ribosome is 18s rRNA. There are 5000 ribonucleotides in 28s rRNA, 160 ribonucleotides in 5.8s rRNA, 120 ribonucleotides in 5s rRNA. Whereas 18s rRNA contains 1800 ribonucleotides.
  6. rRNA is a structural molecule. Whereas tRNA and rRNA are functional molecules.
  7. The units of the ribosome and the rRNA found in them are represented by the Swedberg Unit (S). It shows sedimentation rate of these molecules.


Other types of RNA:
  1. snRNA - Small Nuclear RNA
  2. scRNA - Small Cytoplasmic RNA
  3. Ribozyme - acts like an RNA enzyme.
  4. miRNA - MicroRNA
  5. piRNA - Piwi-interacting RNA
  6. snoRNA - Small Nucleolar RNA
  7. hnRNA - Hetero Nuclear RNA


Role of microRNA (miRNA)
The microRNA (miRNA) contains very few RNA molecules that were recently discovered. These molecules help control gene expression because they can tag mRNA for degradation or inhibit translation into new proteins.

This means that miRNA has the ability to down-regulate or silence genes. Molecular biology researchers consider miRNA important for the treatment of genetic disorders such as cancer, where gene expression can either drive or inhibit the development of the disease.


Frequently Asked Questions.

What is RNA?
Answer : The chain consists of mRNA and tRNA consisting of building blocks called RNA nucleotides. The nucleotides of each of these buildings contain a sugar, called ribose, a high-energy chemical group, called phosphate, and one of four possible "nitrogenous bases" --- ringed or double-ringed. Structures whose background is formed not only from carbon, but also from several nitrogen atoms (see figure). Nucleotides bind to each other through phosphate and sugar groups, forming a "backbone" to which the nitrogenous bases are attached, one for each ribose sugar.


Enlist Four types of Nitrogenous bases of RNA
Answer : In most cases, four bases are found in RNA. Two of these, adenine (A) and guanine (G), have two chemical rings and are called purines. The other two, each containing a chemical ring, cytosine (C) and uracil (U), are called pyrimidines.


What are the Function of mRNA
Answer : Each molecule, or chain, of the mRNA gives instructions to add several "amino acids" to the peptide chain, which becomes a protein. Just as nucleotides are building blocks for RNA, amino acids are making blocks for proteins. Evolution has produced a "genetic code", each containing 20 amino acids coded for a series of three nitrogenous bases in RNA nucleotides. Thus, each triple of RNA nucleotides corresponds to one amino acid, and the order of nucleotides determines the sequence of amino acids that will be added to the peptide chain that make up the protein. While in some cases an amino acid can be represented by multiple nucleotide triples, called codons, each codon on RNA represents only one amino acid. For this reason, the genetic code is called "degenerate".


what are Function of tRNA
Answer : tRNA is the actual translator. The translation of the language of RNA into the language of a protein is possible, as there are many forms of tRNA, each representing an amino acid (protein building block) and capable of linking with an RNA codon. Thus, for example, the tRNA molecule for the amino acid alanine has a region or binding site for allanin and another binding site for three RNA nucleotides, the codon, for allanin.