Ans. mRNA and tRNA :--
mRNA :-- (i) It is a linear and long RNA which constitutes 2-5% of the total RNA contents.
(ii) It brings instructions from the DNA for the formation of particular type of poly-peptide.
(iii) span is very short i.e., 2 minutes to 4 hours, degraded after i translation.
tRNA :-- (i) It is clover like form (two dimensional, Holley 1965). According to Klug 1974, it is reversed 'L' shaped and three dimensional which constitutes about 15% of total RNA content.
(ii) The tRNA is adapter molecule which is meant for transferring amino acids to ribosomes or to mRNA codons for the synthesis of polypeptides.
(iii) Long life span used again and again in translation.
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