Summing up any symposium with the word ''molecu-and enhancers, and, in their perambulations about the genome, they have the potential for turning up the pro-lar'' in its title is a challenging endeavor, given the daily advances in virtually all subdivisions of molecular duction of genes that are not ordinarily expressed in abundance. He illustrated this phenomenon with a science. Trying to cap a conference on molecular anthropology is particularly daunting, especially when number of examples from plants, sea urchins, and humans, in which mobile elements have been inserted the sweep of papers covers almost the entire living world. At first glance, about all that unites the papers into situations where they now control the transcription of assorted genes. in this case is occasional reference to primates, on the one hand, and an enthusiastic appreciation for Morris Gene regulation and its influence on primate evolution were the topics of a paper on a key aspect of the Goodman, the inspirational and genuine molecular anthropologist to whom the symposium was dedicated. evolution of the Ξ²-globin cluster. Thus, most mammals have an array of five clustered genes closely related to Nevertheless, there was an anthropological thread, occasionally frayed, that ran through most of the contri-the Ξ²-chain, one of which is expressed in the embryo.
Additionally, anthropoid primates have a sixth re-butions, and I will do my best to follow it here.
Reasonably enough, the presentations began with cently duplicated gene, encoding the Ξ³-chain, which is expressed in the fetus. What determines the appro-some broad molecular considerations. The human genome, like other vertebrate genomes, is not homoge-priate time of expression for these genes? D. Gumucio and her colleagues used a kind of phylogenetic foot-neous along its chromosomal lengths with regard to its GC content. Rather, as ably described by G. Bernardi printing with synthetic oligonucleotides to distinguish the regulatory elements in the DNA that allow the dif-in the opening paper, it is a mosaic of isochores sharply delineated into segments of the order of 300 kb, which ferential expression. Clearly, there is more to evolution than merely duplicating and modifying genes. Express-themselves have characteristically high or low GC contents. Moreover, genes are not distributed uniformly ing them at the right time and place is critical.
The enormous power of modern megasequencing was throughout the genome, the isochores with the highest GC content being the richest in genes. Perhaps not un-demonstrated by B. F. Koop, who reported on hundreds of kilobases of DNA sequence from a part of the human expectedly, the highest concentrations of ''CpG islands,'' well known to be associated with upstream reg-T-cell receptor. Comparison with the corresponding regions from mouse showed that there has been a surpris-ulatory units for genes, are also found in these GC-rich regions. Bernardi made a strong case for there having ing amount of rearrangement and duplication, despite rather strict sequence conservation locally. The exten-been a significant increase in the overall genomic GC content at the evolutionary junctions of cold-and sive rearrangement was apparent even when genomes of higher primates were compared. The constant writh-warm-blooded vertebrates, as might be warranted by a need for greater stability at higher temperatures, per-ing of DNA is forever spawning new arrangements that offer new faces to the changing world. haps. Remarkably, this presumably adaptive response appears to have occurred on two separate occasions, In a paper discussing the general ramifications of what can emerge from persistent and focused sequenc-once at the reptile-bird junction and again at the divergence leading to mammals.
ing, Hewett-Emmett and Tashian summarized a series of unexpected findings on their favorite enzyme, car-These remarks on the idiosyncrasies of DNA composition were logically followed by a consideration of re-bonic anhydrase. Foremost among these is the fact that the enzyme has evolved independently on three sepa-petitive sequences in DNA, and especially their association with transposable elements. R. Britten pointed rate occasions, each time with a zinc ion at the catalytic center, but with three completely different protein out that many of these elements have strong promoters 266