DNA gets concise by skipping a lot of repetitive stretches
Richard E. Lee Jr.
The smallest known insect genome belongs to an Antarctic midge that has to survive two polar winters as a larva to reach its week or so sexual adulthood. The DNA instructions for Belgica antarctica fit in a mere 99 million of the paired basic chemical units that encode living creatures. That’s a bit more concise than DNA in other small genomes among insects, such as the body louse’s 105 million base pairs.
The Antarctic midge slims its DNA without giving up protein-coding genes —it has an unremarkable 13,500 or so, in a similar range to nematodes. Instead, midge DNA is missing a lot of repetitive stretches found between genes. About 19.4 percent of the midge genome carries codes for making proteins versus only about 1.6 percent in the Aedes aegypti mosquito. Other species, like bladderworts and puffer fish, also minimize genetic repeats. But the midge truncations might have something to do with life under extreme Antarctic conditions, researchers suggest August 12 in Nature Communications.
J.L. Kelley et al. Compact genome of the Antarctic midge is likely an adaptation to an extreme environment. Nature Communications. Published online August 12, 2014. doi: 10.1038/ncomms5611.
A. Yeager. Loblolly sets record for biggest genome. Science News. Vol. 185, May 17, 2014, p. 4.