Genomes from scratch Synthetic infective bacteriophage generated from a random pool of DNA
oligonucleotides By Cathy Holding
The ability to generate synthetic DNA sequences has many potential applications not open when using
conventional cloning techniques, such as investigations into archaeological, extinct, or otherwise
unavailable genes and genomes. In addition, the synthetic generation of entire genomes could
facilitate novel methods of energy production, has pharmaceutical and industrial applications, and
ultimately paves the way to understanding the basics of life itself. The synthesis of large segments
of DNA has until recently been difficult, costly, and time consuming, but in an advanced online
publication of PNAS on November 13, Hamilton Smith and colleagues at the Institute of Biological
Energy Alternatives publish a technique for the in vitro synthesis of 5–6 kb segments of DNA
sequence that is inexpensive, requires minimal manipulation, and can be completed in around a
fortnight (PNAS, November 13, 2003).
As proof of the efficacy of the technique, the authors synthesized the genome of the bacteriophage
phiX174 (ΦX)—a virion containing a circular, single-stranded DNA molecule 5386 bases in length
that infects only a limited number of enteric bacteria—from a pool of synthetic oligonucleotides
and proved both the accuracy of the original source sequence and the accuracy of their own
synthetic sequence by demonstrating infectivity of their construct in the natural host, Escherichia
coli HF4704.
Read the rest at The Scientist.com biomedcentral.com04Open ↗
Ancient 'GM' corn Allelic selection established in ancient crops maintained in modern-day maize By
C L Bishop
The ancestor of modern-day maize (Zea mays) has been the subject of fevered debate since the 1920s,
with the most likely candidate being the wild grass teosinte. It is thought that contemporary maize
arose from a single domestication event of teosinte parviglumis in the Balsas River Basin, Mexico,
as early as 9000 years ago. What is remarkable is that the seeds required dispersal by prehistoric
man. Previous work established that only five genomic regions were responsible for the phenotypic
differences between teosinte and maize. Subsequently, three genes contributing to these differences
have been cloned and characterized—the tb1 and pbf gene products control levels of kernel storage
protein, while the su1 gene encodes a starch debranching enzyme that is involved in corn tortilla
texture. In the November 14 Science, Viviane Jaenicke-Després and colleagues at the Max Planck
Institute for Evolutionary Anthropology compared DNA sequences of the tb1, pbf, and su1 from maize
landraces from the Americas with those isolated from teosinte parviglumis. The authors identified
modern corn alleles present within archaeological samples from 4000 years ago, suggesting that the
genetic modification giving rise to these ancient plants resulted in superior crops that have been
maintained as such for millennia (Science,
302:1206-1208, November 14, 2003).
Kind Regards, Robert Karl Stonjek.