It is not often that the audience at a scientific meeting gasps in amazement during a talk. But that is what happened recently when researchers revealed that they had deleted huge chunks of the genome of mice without it making any discernable difference to the animals. The result is totally unexpected because the deleted sequences included so-called “conserved regions” thought to have important functions.All DNA tends to acquire random mutations, but if these occur in a region that has an important function, individuals will not survive. Key sequences should thus remain virtually unchanged, even between species. So by comparing the genomes of different species and looking for regions that are conserved, geneticists hope to pick out those that have an important function.It was assumed that most conserved sequences would consist of genes coding for proteins. But an unexpected finding when the human and mouse genomes were compared was that there are actually more conserved sequences within the deserts of junk DNA, which does not code for proteins.The thinking has been that these conserved, non-coding sequences must, like genes, be there for a reason. And indeed, one group has shown that some conserved regions seem to affect the expression of nearby genes.
