Which term describes sequences of DNA that do not code for proteins and are removed before protein synthesis?

The term that describes sequences of DNA that do not code for proteins and are removed before protein synthesis is "introns." Introns are segments of a gene that are transcribed into precursor messenger RNA (pre-mRNA) but are not included in the final messenger RNA (mRNA) that gets translated into a protein. During the process of RNA splicing, introns are cut out of the pre-mRNA, and the remaining coding sequences, known as exons, are joined together to form the mature mRNA, which then directs protein synthesis. This process highlights the intricate control of gene expression and the role of non-coding DNA regions in regulating which proteins are produced in a cell.

The other terms are related but do not specifically address the components that are removed before protein synthesis. Noncoding DNA refers broadly to sections of DNA that do not code for proteins, including introns and other non-coding regions, while exons are the coding segments that remain in mRNA. Codons are sequences of three nucleotides in mRNA that specify amino acids in a protein sequence, thus they are not relevant in the context of untranslated DNA sequences.