It is a relatively short period of time since the early 1970s when the first recombinant DNA experiments were carried out. However, huge strides have been made, not only in the development of molecular biology techniques, but also in their practical application. The molecular basis of disease and the new areas of genetic analysis and gene therapy hold great promise. In the past, medical science relied on the measurement of protein and enzyme markers that reflected disease states. It is now possible not only to detect such abnormalities at an earlier stage using mRNA techniques, but also in some cases to predict such states using genome analysis. The complete mapping and sequencing of the human genome and the development of techniques such as DNA microchips will certainly accelerate such events. Perhaps even more difficult is the elucidation of diseases that are multifactorial and involve a significant contribution from environmental factors. One of the best-studied examples of this type of disease is cancer. Molecular genetic analysis has allowed a discrete set of cellular genes, termed oncogenes, to be defined that play key roles in such events. These genes and their proteins are also major points in the cell cycle and are intimately involved in cell regulation (see examples in Table 1). In a number of cancers, well-defined molecular events have been correlated with mutations in these oncogenes and therefore in the corresponding protein. It is already possible to screen and predict the fate of some disease processes at an early stage, a point that itself raises significant ethical dilemmas. In addition to understanding cellular processes, both in normal and disease states, great promise is also held in drug discovery and molecular gene therapy. A number of genetically engineered therapeutic proteins and enzymes have been developed and are already having an impact on disease management. In addition, the correction of disorders at the gene level ( gene therapy ) is also underway. Perhaps one of the most startling applications of molecular biology to date is gene editing and the development of gene modifications methods such as the CRISPR/Cas9 system, which may have a profound impact on treating genetic-based diseases. A number of these developments are indicated in Table 2.
Table1. General classification of oncogenes and their cellular and biochemical functions
Table2. A number of selected examples of targets for gene therapy
The production of modified crops and animals for farming and as producers of important therapeutic proteins is also one of the most exciting developments in molecular biology. This has allowed the production of modified crops, improving their resistance to environmental factors and their stability (Table 3). The production of transgenic animals also holds great promise for improved livestock quality, low-cost production of pharmaceuticals and disease-free or disease-resistant strains. In addition, RNAi has also been shown to be a useful addition in many areas of crop improvement. In the future this may overcome such factors as contamination with agents such as BSE. There is no doubt that improved methods of producing livestock by whole-animal cloning will also be a major benefit. All of these developments do, however, require debate and the many ethical considerations that arise from them require careful consideration.
Table3. Current selected plant/crops modified by genetic manipulation
