The unexpressed non-coding regions of eukaryotic genes are called introns.

Here's why:

* Introns are sections of DNA within a gene that are transcribed into RNA but are later removed before the RNA is translated into protein.

* Exons are the coding regions of a gene that are spliced together to form the final mRNA that is translated into protein.

So, while introns are part of the gene and are transcribed, they don't actually contribute to the final protein product.