I don't know about "highly conserved". If I read the abstract right, the sequences' similarities are at 70% to ours:
We deleted two large non-coding intervals, 1,511 kilobases and 845 kilobases in length, from the mouse genome. ... Together, the two deleted segments harbour 1,243 non-coding sequences conserved between humans and rodents (more than 100 base pairs, 70% identity).I can't find a decent reference to a percentage similarity number for the mouse genome as a whole vs. ours, but 70% doesn't seem like it should be any higher than the overall mouse vs. human figure. I did run across an interesting statement in this article:
"If segments of the genomes of two different organisms have been conserved (meaning the sequences are the same in both) over the millions of years since those organisms diverged, then the DNA sequences within those segments probably encode important biological functions."I suspect that the putative junk DNA regions they knocked out were in fact not highly conserved compared to coding regions.The search for functional DNA sequences that have been conserved between two different organisms across a large distance in evolution is the classical approach to comparative genomics that has been used to interpret the information in the human genome. In order for this technique to work, the conserved functional sequences have to stand out as distinct from the non-functional sequences that were not conserved. That degree of distinction requires the passage of time--lots of it--in order for mutations and the lack of selection pressures to cause the non-functional sequences in the two genomes to drift apart.
For example, mice and humans last shared a common ancestor about 75 million years ago, plenty of time for the non-functional sequences in their respective genomes to go their separate ways. Only about five-percent of the two genomes are conserved and it has been shown that most of the genes and regulatory sequences that have been discovered lie within these conserved DNA segments.
The point is that 1,243 sequences, each over 100 base pairs with 70% identity is a humongus conserved "area". There is something called expectation when sequences are compared by BLAST. I'm pretty sure the expectation for this is close to zero. This is what I got when I took a 110 base sequence from mus musculus cytochrome and compared it to homo sapiens.
Score = 38.2 bits (19), Expect = 3.9
Identities = 19/19 (100%)
Strand = Plus / Plus
Query: 86 atgggccttcttgctcagt 104
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Sbjct: 223143 atgggccttcttgctcagt 223161
The expectation is low but the percent identities are 100%