Final answer:
Heterochromatin in eukaryotic cells is involved in gene regulation by silencing genes and maintaining chromosome structure by reinforcing the integrity of DNA during cell division.
Step-by-step explanation:
In eukaryotic cells, heterochromatin plays several key functional roles, including gene regulation and maintaining chromosome structure. Heterochromatin is a densely packed form of DNA, which makes certain regions of the genome less accessible to the machinery involved in transcription. This density contributes to the silencing of genes within these regions and plays a critical role in regulating the genes that are turned 'on' or 'off'. Additionally, the condensed nature of heterochromatin aids in reinforcing the overall structure of chromosomes, thereby safeguarding the integrity of the DNA during cell division.