The type of RNA called the blueprint for constructing a protein is messenger RNA (mRNA).

Here's why:

* mRNA carries the genetic code from DNA to the ribosomes. Ribosomes are the cellular machinery responsible for protein synthesis.

* The sequence of nucleotides in mRNA dictates the sequence of amino acids in the protein. This sequence is determined by the genetic code, which translates each three-nucleotide codon into a specific amino acid.

So, mRNA acts as the intermediary between the DNA's genetic instructions and the protein-building process.