tRNA is a single stranded molecule consisting of a backbone of ribose sugar and phosphates bonded to each other and with one nitrogenous base (Uracil, guanine, adenine and cytosine) bonded to each sugar. The strand is folded into a clover shape (bonded by intramolecular base-pairing) and has an anticodon at one end consisting of a specific three base long sequence. At the other end, an amino acid is bonded to the molecule via an ester bond that can be easily hydrolised).
mRNA is also a single stranded polynucleotide with a backbone of phosphate and ribose sugar with a nitrogenous base (could be uracil, guanine, cytosine or adenine) bonded to each sugar. The molecule is long and has the complementary base sequence to that of the gene it has been transcribed from.