(August 2004) Development of mass spectrometry began with J.J. Thomson’s vacuum tube, with which, in the early part of the 20th century, he demonstrated the existence of electrons and “positive rays.” Thomson observed that the new technique could also be used by chemists to analyze chemicals. Despite this far-sighted observation, the primary application of mass spectrometry remained in the realm of physics for nearly thirty years. It was used to discover a number of isotopes, to determine the relative abundance of isotopes, and to measure isotope masses. These important fundamental measurements laid the foundation for later developments in diverse fields…

(August 2004) A cell functions by using its genes to produce proteins and although each cell within an organism will usually contain the same set of genes, there are significant differences in which genes are activated and how they are controlled. This is idea is easy to digest when you think about how a single-celled embryo goes on to produce all kinds of different tissues. At any rate, the mechanism by which genes are utilized is the same for all cells and involves the transcription of a gene into mRNA before being translated into a protein. The production of mRNA…

We need to appreciate beer more. Alcohol has a long history in human affairs, and has been important in purifying and preserving food and drink, and in making our parties livelier. We owe it all to a tiny little microorganism, Saccharomyces cerevisiae, which converts complex plant sugars into smaller, simpler, more socially potent molecules of ethanol. This is a remarkable process that seems to be entirely to our benefit (it has even been argued that beer is proof of the existence of God*), but recent research has shown that the little buggers do it all entirely for their own selfish…

Bt corn, a genetically modified organism (GMO), has been both the poster-child and thorn-in-the-side of the plant biotechnology industry from the late 1990’s to present. There are several versions of this transgenic crop that each have a gene from an insect pathogen, Bacillus thuringiensis (Bt), which encodes a protein toxic to the European corn borer (ECB), an insect pest that eats and destroys corn stems (see Figure 1). Bt corn has proven effective in reducing crop damage due to ECB, yet public opposition to Bt corn has escalated amid fears of human health and environmental risks associated with the production…

(August 2004) Genetic Carrying Handles: Cloning Vectors In order to clone a gene, its DNA sequence must be attached to some kind of carrier, also made of DNA, that can take it into the cell. Biologists call these carriers vectors. A vector acts like a handle for the DNA, and it also contains other tools such as an origin of replication and a selective marker. The origin of replication is a sequence of DNA that the host cell recognizes that allows it to make more copies of the clone DNA sequence. This origin sequence is where the cell begins copying…

(August 2003) Messenger RNA (mRNA) is a single stranded molecule that is used as the template for protein translation. It is possible for RNA to form duplexes, similar to DNA, with a second sequence of RNA complementary to the first strand. This second sequence is called antisense RNA (Figure 1). The formation of double stranded RNA can inhibit gene expression in many different organisms including plants, flies, worms and fungi. Figure 1 Formation of antisense RNA blocks translation. Co-Suppression The first discovery of this inhibition in plants was more than a decade ago and occurred in petunias. Researchers were trying…

(August 2004) Construction a knockout mouse For decades researchers have tried to create tools that allowed for precise control over a specific gene in order to study its function. In the early 1980’s a breakthrough technology known as transgenics or gene transfer was developed [1]. This new technology involved the process of pronuclear microinjection, a method involving the injection of genetic material into the nuclei of fertilized eggs (Figure 1). Following injection, DNA would incorporate into the genome of the cell. The transformed fertilized eggs were then injected back into pregnant females and brought to term. A major downfall of…

(August, 2003) The first inklings of genetic theory can be traced back to a common human experience: the recognition that a child has features similar to those of its parents. This ancient observation is actually one of the cornerstones of genetics and its subsequent offspring, molecular biology. For centuries there was little evidence beyond the anecdotal that transmitted inheritance was a reasonable theory. Though it seemed sensible that a child with the same appearance as its parents likely received these characteristics from them, little evidence supported the notion and instead a good deal of confusion surrounded it. Part of the…

Milestones in DNA research The discovery of DNA structure in 1953 was the starting point of a real scientific and cultural revolution, the ending of which is difficult to predict. The discovery and use of enzymes that copy, cut and join DNA molecules in cells was the next step in this revolutionary course. The development of two major techniques contributed further to this already vertiginous process: the manual DNA sequencing method, which appeared in 1975, and the discovery of the polymerase chain reaction (PCR) in 1985, which allows the million-fold amplification of DNA sequences. A natural consequence of these two…