Final answer:
Evidence suggests that the large amount of excess junk DNA in a genome may serve an important function, as discovered miRNA genes, Inc RNAs, and repetitive DNA sequences like transposons have been found to have specific functions related to gene regulation and genetic diversity.
Step-by-step explanation:
The idea of the large amount of excess junk DNA in a genome serving an important function is supported by several lines of evidence. First, the discovery of miRNA genes and Inc RNAs suggests that there is a far greater amount of functional DNA in the genome than previously thought. Second, studies have found that a significant portion of noncoding DNA, once considered junk DNA, actually plays a role in regulating gene expression, DNA packaging, and chromosomal stability. Lastly, repetitive DNA sequences like transposons, which were once thought to be junk, have been found to have specific functions that contribute to genetic regulation and increasing genetic diversity.