Posted on Tuesday 27 May 2003

The Dark Side of the Genome While we speak of matters dark:

Researchers shine their lights on noncoding sequence

The dark side of the moon is a misnomer. Light reaches la luna's entire surface, but one half is unviewable from Earth. The human genome, the now essentially decoded map of life, likewise has a light side--the genes encoding mRNA and protein--and a dark side, which is coming into view for the first time. The dark side encompasses more than its opposite: The majority of the genome comprises intronic regions, stretches of repeat sequence, and other assorted gibberish that has attained the ignoble dubbing, "junk."

The first exploratory missions to the human genome's faceted surface are turning up traces regarding the extent of the junk. At a recent National Human Genome Research Institute (NHGRI) conference, numerous presenters invoked Sydney Brenner's classic distinction: "Garbage you throw away and junk you keep, because you think you might want to do something useful with it, and of course you never do."

Comparative, computational, and experimental studies can shine light on these unexplored DNA elements. Some are known regulatory stretches; others encode RNAs but offer scarce hints at their function. Eric Green, chief of NHGRI's genome sequencing branch, says, "I think the challenge is going to be in the nongenic, functional portion of the genome."

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