Size
of
Messenger
RNA
-
mRNA - The molecular weight of an average sized mRNA molecule is about 500,000, and its sedimentation coefficient is 8S. It should be noted however, that mRNA varies greatly in length and molecular weight. Since most proteins contain at least a hundred amino acid residues, mRNA must have at least 100 X 3= 300 nucleotides on the basis of the triplet code.
In E. coli the average mRNA strand has 900 to 1,500 nucleotide units which would code polypeptide chains of 300-500 amino acids. Molecules containing 12,000 nucleotide units are also known.
