mRNA (messenger RNA) is used by a cell to carry genetic information from DNA to the ribosomes, where proteins are synthesized. Here's a breakdown of how it works:

1. Transcription: DNA, which contains the genetic code, is transcribed into mRNA in the nucleus. This process involves the enzyme RNA polymerase, which uses the DNA as a template to create a complementary mRNA strand.

2. mRNA Processing: The newly transcribed mRNA undergoes modifications, including splicing (removing non-coding regions), capping, and adding a poly-A tail. These modifications help protect the mRNA and ensure it can be translated by ribosomes.

3. Translation: The processed mRNA travels from the nucleus to the cytoplasm, where it encounters ribosomes. Ribosomes are molecular machines that "read" the mRNA sequence and translate it into a chain of amino acids. This process is called translation.

4. Protein Synthesis: Each three-nucleotide codon on the mRNA corresponds to a specific amino acid. Ribosomes use this information to assemble a chain of amino acids, forming a protein.

In summary, mRNA acts as a messenger, carrying the genetic blueprint from DNA to the ribosomes, where it is used to build proteins.