In the past, much of the non-coding DNA in the human genome was referred to as "junk DNA" because its function was unknown. However, recent research has revealed that much of this DNA actually plays important roles in the structure and function of the genome. Some of the functions of non-coding DNA include:

- Gene regulation: Non-coding DNA can act as regulatory elements that control the expression of genes. For example, enhancers are regions of DNA that bind to proteins called transcription factors, which then promote the transcription of nearby genes.

- Genome organization: Non-coding DNA can help to organize the genome into distinct regions, such as chromosomes and gene clusters. This organization is essential for the proper functioning of the cell.

- Telomere maintenance: Telomeres are repeating sequences of DNA at the ends of chromosomes. They protect the chromosomes from degradation and fusion with other chromosomes. Telomeres are maintained by an enzyme called telomerase, which uses non-coding DNA as a template to synthesize new telomere DNA.

- RNA production: Some non-coding DNA is transcribed into RNA molecules that do not code for proteins. These RNA molecules can have a variety of functions, such as regulating gene expression and participating in cellular processes.

These are just a few of the important functions of non-coding DNA. As research continues, we are likely to learn even more about the vital roles that this DNA plays in the proper functioning of the human genome.