Final answer:
The non-coding segments of eukaryotic DNA are called introns, which are removed from pre-mRNA in the nucleus during splicing, while the coding segments are called exons.
Step-by-step explanation:
The non-coding segments of a stretch of eukaryotic DNA are known as introns. In eukaryotic genes, these introns are interspersed with coding regions called exons. While exons are expressed and remain coding for proteins, introns do not code for proteins and are removed from the pre-mRNA during the process of splicing. The removal and subsequent degradation of introns occur within the nucleus, ensuring that the mature mRNA, which is translated into proteins, contains only the exons.
Introns play a role in gene regulation and can vary in number and size depending on the gene. Although their exact functions are sometimes unclear, it's known that proper excision of introns is critical: any errors in the splicing process can result in a faulty protein. This interspersed structure of introns and exons means that genes in eukaryotes can often be much larger than the proteins for which they code.