Today, EvoLiteracy News picks are about sexual dimorphism –apparently driven by female mate choice– in Stegosaurus dinosaurs. Also, research just published about editing DNA in human zygotes has generated numerous editorials in science journals (we’ll hear more about it in the upcoming months). The Hubble Telescope celebrates its 25th anniversary. And a powerful video by Stated Clearly Animations on “What is The Evidence For Evolution” — GPC.
Sexual Dimorphism in the Plated Dinosaur Stegosaurus? Yes, why not. Study just published in PLoS ONE.
Author E. T. Saitta summarizes the research as follows: “Conclusive evidence for sexual dimorphism in non-avian dinosaurs has been elusive… [D]imorphism in the shape of the dermal plates of Stegosaurus mjosi (Upper Jurassic, western USA)… is most likely a sexually dimorphic feature. One morph possessed wide, oval plates 45% larger in surface area than the tall, narrow plates of the other morph. Intermediate morphologies are lacking as… analysis supports marked size- and shape-based dimorphism… Taphonomy of a new quarry in Montana (JRDI 5ES Quarry) shows that at least five individuals were buried in a single horizon and were not brought together by water or scavenger transportation. This new site demonstrates co-existence, and possibly suggests sociality, between two morphs that only show dimorphism in their plates. Without evidence for niche partitioning, it is unlikely that the two morphs represent different species. Histology of the new specimens in combination with studies on previous specimens indicates that both morphs occur in fully-grown individuals. Therefore, the dimorphism is not a result of ontogenetic change. Furthermore, the two morphs of plates do not simply come from different positions on the back of a single individual. Plates from all positions on the body can be classified as one of the two morphs, and previously discovered, isolated specimens possess only one morph of plates. Based on the seemingly display-oriented morphology of plates, female mate choice was likely the driving evolutionary mechanism rather than male-male competition. Dinosaur ornamentation possibly served similar functions to the ornamentation of modern species…” For complete study go to PLoS ONE.
Gene Editing in Human Zygotes? Again, yes, and we’ll hear more debate about this type of research in the social media and science editorials.
Liang et al. (total sixteen authors) just published an article in the journal Protein & Cell about DNA-engineering in human zygotes, specifically of genes involved in blood disorders. The authors summarized the research as follows: “Genome editing tools such as the clustered regularly interspaced short palindromic repeat (CRISPR)-associated system (Cas) have been widely used to modify genes in model systems including animal zygotes and human cells, and hold tremendous promise for both basic research and clinical applications. To date, a serious knowledge gap remains in our understanding of DNA repair mechanisms in human early embryos, and in the efficiency and potential off-target effects of using technologies such as CRISPR/Cas9 in human pre-implantation embryos. [Liang et al.] used tripronuclear (3PN) zygotes to further investigate CRISPR/Cas9-mediated gene editing in human cells. [The authors] found that CRISPR/Cas9 could effectively cleave the endogenous β-globin gene (HBB). However, the efficiency of homologous recombination directed repair (HDR) of HBB was low and the edited embryos were mosaic. Off-target cleavage was also apparent in these 3PN zygotes as revealed by the T7E1 assay and whole-exome sequencing. Furthermore, the endogenous delta-globin gene (HBD), which is homologous to HBB, competed with exogenous donor oligos to act as the repair template, leading to untoward mutations. [The] data also indicated that repair of the HBB locus in these embryos occurred preferentially through the non-crossover HDR pathway. Taken together, [the study] highlights the pressing need to further improve the fidelity and specificity of the CRISPR/Cas9 platform, a prerequisite for any clinical applications of CRSIPR/Cas9-mediated editing.” For complete study go to Protein & Cell; for criticisms go to Nature (Chinese Scientists Genetically Modify Human Embryos).
According to Nature magazine, Liang et al. “attempted to modify the gene responsible for β-thalassaemia, a potentially fatal blood disorder, using a gene-editing technique known as CRISPR/Cas9… [The researchers] injected 86 embryos and then waited 48 hours, enough time for the CRISPR/Cas9 system and the molecules that replace the missing DNA to act — and for the embryos to grow to about eight cells each. Of the 71 embryos that survived, 54 were genetically tested. This revealed that just 28 were successfully spliced, and that only a fraction of those contained the replacement genetic material… [The researchers] also found a surprising number of ‘off-target’ mutations assumed to be introduced by the CRISPR/Cas9 complex acting on other parts of the genome. This effect is one of the main safety concerns surrounding germline gene editing because these unintended mutations could be harmful. The rates of such mutations were much higher than those observed in gene-editing studies of mouse embryos or human adult cells.” For more discussion go to Nature.
25 years of The Hubble Telescope. One of NASA’s amazing scientific achievements… An acute eye on the cosmos!
After twenty five years in operation, and five servicing missions (1993, 1997, 1999, 2002, 2009), NASA’s Hubble Telescope continues to send images of impressive quality. Here is NASA’s overview of The Hubble Telescope (for detailed information go to NASA’s Hubble):
Hubble has made more than 1.2 million observations since its mission began in 1990.
Astronomers using Hubble data have published more than 12,800 scientific papers, making it one of the most productive scientific instruments ever built.
Hubble does not travel to stars, planets or galaxies. It takes pictures of them as it whirls around Earth at about 17,000 mph.
Hubble has traveled more than 3 billion miles along a circular low Earth orbit currently about 340 miles in altitude.
Hubble has no thrusters. To change pointing angles, it uses Newton’s third law by spinning its wheels in the opposite direction. It turns at about the speed of a minute hand on a clock, taking 15 minutes to turn 90 degrees.
Hubble has the pointing accuracy of .007 arc seconds, which is like being able to shine a laser beam on a dime 200 miles away.
Outside the haze of our atmosphere, Hubble can see astronomical objects with an angular size of 0.05 arc seconds, which is like seeing a pair of fireflies in Tokyo from your home in Maryland.
Hubble has peered back into the very distant past, to locations more than 13.4 billion light years from Earth.
The Hubble archive contains more than 100 Terabytes, and Hubble science data processing generates about 10 Terabytes of new archive data per year.
Hubble weighed about 24,000 pounds at launch and currently weighs about 27,000 pounds following the final servicing mission in 2009 – on the order of two full-grown African elephants.
Hubble’s primary mirror is 2.4 meters (7 feet, 10.5 inches) across.
Hubble is 13.3 meters (43.5 feet) long — the length of a large school bus.
For collection of images go to Hubble Gallery.
Video Animation: this time “What is the evidence for Evolution?” by Stated Clearly Animations