Question

Why do cells need both tRNA and mRNA

Answer 1

mRNA is copied directly from DNA and just a long string of nucleotides that contains the "message" - the protein that needs to be made. tRNA is a different chain of nucleotides that "reads" this message in groups of three nucleotides, and brings an amino acid corresponding to that group of three which is then added into the protein being built.

Answer 2

for protein synthesis..