The pairing of mRNA and tRNA to make a protein, known as translation, occurs primarily in the ribosomes.

Here's a breakdown:

* mRNA (messenger RNA): Carries the genetic code from DNA in the nucleus to the ribosomes in the cytoplasm.

* tRNA (transfer RNA): Each tRNA molecule carries a specific amino acid and has an anticodon that matches a specific codon on the mRNA.

* Ribosomes: These complex structures are responsible for reading the mRNA sequence and assembling the amino acids in the correct order to form a protein.

Therefore, translation, the process of protein synthesis, occurs in the ribosomes.