VPB 112: General Veterinary Biochemistry (1+1)

MESSENGER RNA (m RNA)

• They constitute 5 – 10% of the total RNA concentration in the cell.
• m RNA carries genetic information from the DNA to the cytoplasm, where it is used as a template for protein synthesis.
• m RNA has high molecular weight with a relatively short half – life.
• Two important features are,
  • The presence of a cap (7 – methyl guanosine triphosphate) at the 5’ end,
  • A poly A tail at 3’ end.
• The cap structure protects the 5’ terminus from the action of exonuclease.
• The poly A tail is believed to have a role in transporting mRNA out of the nucleus. Note that not all mRNA have poly A tail.
• Functions of m RNA
• m RNA acts as a template for protein synthesis. The codons of m RNA determine the amino acid sequence of protein.
• It interacts with the smaller subunit of the ribosome to initiate protein synthesis.
• The anticodon of aminoacyl t RNA binds with the codon of m RNA by following the base pairing rule.
• When synthesis is completed, the terminating codon,UAA, UGA and UAG causes the release of polypeptide chain.