Final answer:
It is true that the vast majority of the eukaryotic genome does not encode functional genes, with only about 1-2% representing protein-coding genes. The rest includes non-coding DNA with various roles, challenging the previous notion of 'junk DNA'. Non-coding regions can influence gene expression and play a role in maintaining chromosome structure.
Step-by-step explanation:
The vast majority of the eukaryotic genome does not encode for functional genes; this is indeed true. In eukaryotes, only about 1-2% of the genome actually encodes protein-coding genes. The rest of the genome contains non-coding DNA, which includes elements such as transposons, introns within genes, regulatory sequences, and other DNAs that were traditionally thought to be 'junk' because they do not code for proteins.
However, the term 'junk DNA' can be misleading as research has shown that non-coding DNA can have important functions. For instance, some non-coding DNA is involved in regulating gene expression, maintaining chromosome structure, and the formation of noncoding RNA molecules. Transposons, once considered purely selfish DNA existing only to replicate themselves, also play roles in genome evolution and regulation.
The genome of prokaryotic organisms, unlike eukaryotic ones, generally involves less non-coding DNA and their genes are often organized in operons, allowing for coordinated regulation of gene expression. By contrast, eukaryotic genomes contain many introns, and generally show greater complexity in the regulation of gene expression, including epigenetic mechanisms and post-translational modifications.