What is microRNA (miRNA)?

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What is microRNA (miRNA)? Blog Image


Scientists recently identified a single, small strand of microRNA, or miRNA, that plays a crucial role in fighting cancer.

About microRNA (miRNA):

  • MicroRNAs (miRNAs) are a class of non-coding RNAs that play important roles in regulating gene expression.
  • Gene expression refers to whether a particular gene is making too much, too little or the normal amount of its protein at a particular time.
  • Molecules of miRNA are found in cells and in the bloodstream. 
  • They are typically composed of approximately 21 to 24 nucleotides, making them much smaller than messenger RNAs (mRNAs), which carry instructions for protein synthesis. Their small size allows them to bind to specific target mRNAs.
  • How does miRNA control gene expression?
    • miRNA controls gene expression mainly by binding with messenger RNA (mRNA) in the cell cytoplasm. 
    • Instead of being translated quickly into a protein, the marked mRNA will be either destroyed and its components recycled, or it will be preserved and translated later.
    • So, if the level of a particular microRNA is underexpressed (its level in the cell is abnormally low), the protein it normally regulates may be overexpressed (its level will be unusually high in the cell); if the microRNA is overexpressed (its level is unusually high), its protein will be underexpressed (its level will be unusually low).
  • Biological Functions:
    • They play critical roles in various biological processes, including development, cell differentiation, proliferation, and apoptosis (programmed cell death).
    • They are involved in maintaining cellular homeostasis and responding to environmental cues.
  • Disease Implications:
    • Alteration in miRNA expression results in changes in the profile of genes involving a range of biological processes, contributing to numerous human disorders.
    • With high stability in human fluids, miRNAs in the circulation are considered as promising biomarkers for diagnosis, as well as prognosis of disease. 


What is RNA?

  • RNA, or Ribonucleic Acidis a molecule that plays a central role in various biological processes, particularly in the transfer of genetic information and the synthesis of proteins.
  • It is a macromolecule similar to DNA (Deoxyribonucleic Acid) in many ways but differs in its structure and functions.
  • RNA is composed of nucleotide units, just like DNAUnlike DNA, however, RNA is most often single-stranded.
  • Function:
    • The primary function of RNA is to convey genetic information from DNA and use that information to guide the synthesis of proteins.
    • This process involves transcription, where a complementary RNA strand is synthesized based on a DNA template, and translation, where the information encoded in the RNA is used to assemble a specific sequence of amino acids into a protein.


Key Facts about mRNA:

  • Messenger RNA (mRNA) is a type of single-stranded RNA involved in protein synthesis.
  • mRNA is made from a DNA template during the process of transcription.
  • The role of mRNA is to carry protein information from the DNA in a cell’s nucleus to the cell’s cytoplasm (watery interior), where the protein-making machinery reads the mRNA sequence and translates each three-base codon into its corresponding amino acid in a growing protein chain.
  • So mRNA really is a form of nucleic acid which helps the human genomewhich is coded in DNA, to be read by the cellular machinery.


Q1) What is DNA?

DNA, or Deoxyribonucleic Acid, is a molecule that carries most of the genetic instructions used in the growth, development, functioning, and reproduction of all known living organisms and many viruses. It is often referred to as the "building block of life" because of its central role in heredity and genetics.

Source: Study shows a microRNA crucial for fighting cancer