Here's why:

* DNA contains the genetic code: DNA holds the instructions for building and maintaining an organism. These instructions are written in the form of genes.

* RNA copies the instructions: RNA is a messenger molecule that copies the instructions from DNA. It then carries these instructions to the ribosomes, which are the protein-making factories of the cell.

* Ribosomes translate the instructions: Ribosomes read the RNA instructions and use them to assemble amino acids into proteins.

So, RNA acts like a temporary copy of the DNA blueprint, providing the ribosomes with the specific instructions needed to build proteins.