Here’s a collection of news items that deserve quick notice:
- Mars Rumbles: Mars still has minor earthquakes, says Space.com, That’s without plate tectonics, “But scientists don’t know exactly how Mars is constructed.” The Mars Exploration Rovers, meanwhile, awaking from a winter’s nap, are still gathering science data long past their expected lifetime. Evidence for past water is being claimed, even though it would have been loaded with epsom salt. Mars Express has photographed the southern highlands, an area of thick volcanic ash deposits, wind-blown dust, and dust devils.
- A-Maize-ing Genes: The genome of maize (corn) shows some surprises, according to EurekAlert. It has 59,000 genes, and 22% of them are unique compared to closely related species. That’s more difference than between apes and humans. “It looks like significant evolutionary change happened in a relatively short time,” and maybe there was a merger in corn’s past. Or so the story goes. “Plants are continually faced with a variety of seasonal challenges and assaults by a series of different pests which may well lead to evolution on a fast track.” Makes sense when you don’t think about it.
- Molecular Clock Fixed? Nature Science Update reports on a French team that developed a new computer model for getting the so-called “molecular clock” – the rate genes mutate – to correlate with the fossil record (see 04/20/2004 headline). They calibrated assumed evolutionary changes in the genes to six fossil species, and then built an evolutionary tree based on it. Not all are convinced, though. In one case, the tree says that a red alga appeared after its fossil.
- Cave Dating: In Earth and Planetary Science Letters Oct. 15, pp. 265-273, an international team dated aragonite formations in a South African cave. They extracted thin cores from two speleothems. They claimed the cores correlate with climate, but there were anomalies. The trace minerals don’t correlate with rainfall, the cores don’t correlate with temperature, and the two stalactites don’t correlate with each other; one outgrew the other six-fold in an inferred 11-year period. This led them to conclude that “the constant speleothem growth rate we assume is simplistic. The growth rate of the speleothem undoubtedly varies within an annual cycle (growing faster in the rainy season and slower over the dry season) and between different years (growing more in wet years and less in drier ones).”
- DNA Repair Team Can Dance: An article in Cell last month (118:6, 17 Sep 2004, 666-668, http://dx.doi.org/10.1016/j.cell.2004.09.006) described what your DNA repair team (see 01/04/2002 headline) does as a sophisticated kind of ballet, with both orchestra and dancers: “Repair of damaged DNA is a dynamic process that requires careful orchestration of a multitude of enzymes, adaptor proteins, and chromatin constituents…. ” Double-stranded DNA breaks are particularly deadly, but the repairmen, like NYFD heroes, know just what to do, and they can dance:
But how is the multifaceted DSB response “choreographed” so that each molecular “dancer” involved knows when to arrive on the stage, how long and with whom to perform, and when to give way to those that are scheduled to follow? Amazingly, nature has provided cells with a score for a fascinating play called “DNA repair.” Although we have known some of the “dancers” for quite awhile, only now are we actually beginning to see the performance unfold in front of our eyes.
The authors refer to a paper in the same issue by Columbia University scientists, Michael Lisby et al., entitled “Choreography of the DNA Damage Response.” A related story using the choreography metaphor was posted on EurekAlert.
- Junk DNA Promoted: Another story strengthens the case that there is no such thing as “junk DNA” (see 05/27/2004 and 05/23/2003 headlines). A story posted on EurekAlert says that mobile elements called retrotransposons, long thought to be junk from retroviruses that propagate at random in the genome, actually provide “ a large repository of start sites for initiating gene expression” that is apparently very important for developing embryos. “Therefore, more than one third of the mouse and human genomes, previously thought to be non-functional, may play some role in the regulation of gene expression and promotion of genetic diversity.” See also the writeup in Science News 166:16, week of Oct. 16, 2004, p. 243.
- Fossil Fool’s Gold: A paper in Geology this month examines the fine preservation of China’s Chengjiang fossils (see 07/22/2004 headline) and suggests that pyrite was involved. “The apparent explosive diversification of animal life in the Cambrian is one of the most significant events in the history of life and continues to be controversial,” the paper begins. Another paper in the same issue that describes a discovery of Early Cambrian bilaterian embryos and larvae from China states, “In contrast to the Precambrian, evidence for the structural diversity of embryos and larvae in Cambrian strata is mounting.”
- Flip & Flap over ID Paper: The journal that published Stephen Meyer’s intelligent design paper (see 09/24/2004 headline) has now issued a statement that the article should not have been published. To Mark Hartwig writing in Access Research Network’s Weekly Wedge Update, though, this can hardly help their reputation. Meanwhile, the Discovery Institute continues to publish line-by-line refutations of criticisms coming from pro-Darwin forces.
- Fall Colors Delight Tourists, Confuse Scientists: When leaves turn red and yellow, there’s a “reason for the season,” says National Geographic News, but then fails to find it. Yellow is explained by the plant shutting down chlorophyll (green) production, which otherwise swamps the yellow color that is always present. But production of xanthophylls (red) is costly; is it for sunscreen? Antioxidants? Fungal protection? No one knows for sure why deciduous forests turn a riot of color in the fall (see 10/19/2001 headline). One thing is for sure: humans like it.