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These are differentiating mouse embryonic stem cells (green = mesoderm progenitor cells, red = endoderm progenitor cells). The microRNAs identified in this study block endoderm formation, while enhancing mesoderm formation. An embryo is an amazing thing. From just one initial cell, an entire living, breathing body emerges, full of working cells and organs. It comes as no surprise that embryonic development is a very carefully orchestrated process—everything has to fall into the right place at the right time. Developmental and cell biologists study this very thing, unraveling the molecular cues that determine how we become human. "One of the first,...

A new concept making its way through the scientific community holds that just a few key changes in the right genes will result in a whole new life form as different from its progenitor as a bird is from a lizard![1] This idea is being applied to a number of key problems in the evolutionary model, one of which is the lack of transitional forms in both the fossil record and the living (extant) record. The new concept supposedly adds support to the "punctuated equilibrium" model proposed by the late Harvard paleontologist Stephen J. Gould. Dr. Gould derived his ideas...

Researchers have developed a new way to see where the molecules are active Researchers have illuminated a once-hidden developmental process. A fluorescent signal pinpoints the activity of a protein in fruit flies, allowing researchers to see exactly when and where this protein does its job. “The idea of watching life at the molecular level within a cell in an intact organism is really fascinating,” says study coauthor Akira Chiba. The protein, called Cdc42, is present everywhere in the developing fruit fly and controls the production of genes, among other things. But Cdc42 is only active at certain times in certain...