Which part of the DNA does NOT code for proteins?

The correct answer identifies introns as the part of DNA that does not code for proteins. Introns are non-coding sequences within a gene that are transcribed into pre-mRNA but are removed during the RNA splicing process before translation into a protein. While they may play roles in regulating gene expression and post-transcriptional modifications, they do not contribute directly to the amino acid sequence of proteins.

On the other hand, extrons refer to the coding sequences of a gene that remain in the mature mRNA after splicing and are translated into proteins. Ribozymes are RNA molecules with catalytic properties that can perform specific biochemical reactions, often related to RNA processing rather than coding for proteins. Codons are sequences within the mRNA that correspond to specific amino acids during translation, and they are explicitly derived from the exons of a gene. Thus, these components are all involved in the coding or functional roles of RNA/proteins, making introns the distinct choice that does not directly code for any protein.