Researchers deleted large portions of junk DNA from the mouse genome and created mice with the altered genome. No adverse effects were detected, indicating that perhaps non-coding DNA may in fact be useless.
Nature 431, 988 - 993 (21 October 2004); doi:10.1038/nature03022
Megabase deletions of gene deserts result in viable mice
MARCELO A. NÓBREGA et al.
The functional importance of the roughly 98% of mammalian genomes not corresponding to protein coding sequences remains largely undetermined1. Here we show that some large-scale deletions of the non-coding DNA referred to as gene deserts2-4 can be well tolerated by an organism. We deleted two large non-coding intervals, 1,511 kilobases and 845 kilobases in length, from the mouse genome. Viable mice homozygous for the deletions were generated and were indistinguishable from wild-type littermates with regard to morphology, reproductive fitness, growth, longevity and a variety of parameters assaying general homeostasis. Further detailed analysis of the expression of multiple genes bracketing the deletions revealed only minor expression differences in homozygous deletion and wild-type mice. Together, the two deleted segments harbour 1,243 non-coding sequences conserved between humans and rodents (more than 100 base pairs, 70% identity). Some of the deleted sequences might encode for functions unidentified in our screen; nonetheless, these studies further support the existence of potentially 'disposable DNA' in the genomes of mammals.