The untranslated region (UTR) refers to segments of mRNA that are

• A. not translated into protein
• B. translated into protein
• C. structurally important but not transcribed
• D. located in the nucleus

Answer: (A)

Untranslated regions are the parts of an mRNA that do not encode amino acids. They flank the coding sequence, appearing as the 5' untranslated region before the start codon and the 3' untranslated region after the stop codon. Because they do not become part of the protein, these regions are transcribed into RNA but are not translated, while the coding sequence is what actually specifies the protein. The UTRs play important regulatory roles: they influence how efficiently ribosomes initiate translation, affect mRNA stability, localization, and interactions with RNA-binding proteins or microRNAs. They are part of the transcript from DNA and are present in the mature mRNA that operates in the cytoplasm, not restricted to the nucleus.