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Definition of Ribonucleic acid (RNA)

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

Ribonucleic acid (RNA): A nucleic acid molecule similar to DNA but containing ribose rather than deoxyribose. RNA is formed upon a DNA template. There are several classes of RNA molecules.

They play crucial roles in protein synthesis and other cell activities:

  • Messenger RNA (mRNA) is a type of RNA that reflects the exact nucleoside sequence of the genetically active DNA. mRNA carries the "message" of the DNA to the cytoplasm of cells where protein is made in amino acid sequences specified by the mRNA.
  • Transfer RNA (tRNA) is a short-chain type of RNA present in cells. There are 20 varieties of tRNA. Each variety combines with a specific amino acid and carries it along (transfers it), leading to the formation of protein with a specific amino acid arrangement dictated by DNA.
  • Ribosomal RNA (rRNA) is a component of ribosomes. Ribosomal RNA functions as a nonspecific site for making polypeptides.

Reviewed on 12/27/2018

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