Here's why:
* Transcription: DNA contains the genetic code, but it stays safely tucked away in the nucleus of the cell. mRNA acts as a messenger, copying the genetic code from DNA and carrying it out of the nucleus to the ribosomes where protein synthesis happens.
* Translation: At the ribosomes, mRNA's sequence of nucleotides (A, U, G, C) is read in groups of three called codons. Each codon corresponds to a specific amino acid.
* Amino Acid Chain: tRNA molecules (transfer RNA) bring the corresponding amino acids to the ribosome, where they are linked together according to the mRNA sequence, forming a polypeptide chain (a protein).
In short, mRNA is the crucial intermediary that links the genetic information in DNA to the process of building proteins.
