What does the term 'intron' refer to in the context of gene sequences?

The term 'intron' refers specifically to a non-coding region of a gene that is not expressed in the final messenger RNA (mRNA) molecule that is translated into protein. During the process of transcription, both coding sequences (exons) and non-coding sequences (introns) are initially transcribed into a precursor mRNA. Subsequently, introns are removed through a process called splicing before the mRNA is translated into a protein, while the exons are joined together to form the mature mRNA. This process is crucial for the proper expression and function of genes, as introns can play roles in gene regulation and alternative splicing but do not translate into amino acids in the final protein product. Therefore, recognizing introns as non-coding regions that are not part of the expressed gene is essential for understanding the complexities of gene expression and protein synthesis.