The DNA that codes for ribosomes is known as ribosomal DNA (rDNA). This type of DNA contains the genetic instructions necessary for the synthesis of ribosomal RNA (rRNA), which is a critical component of ribosomes. Ribosomes are essential for protein synthesis in all living organisms, as they facilitate the translation of mRNA into proteins. The structure of rDNA includes multiple repetitive sequences, which are often organized in clusters on specific chromosomes, allowing for efficient production of rRNA during cell growth and division.