TABLE OF CONTENTS As we progress beyond the first generation of transgenic crops, it may be useful to take stock of the potential for the development of new types of transgenic crops over the next decade or so. The emerging developments in genomics, proteomics and bioinformatics may allow for some radical modifications of plant architecture, growth habit and composition, which we shall consider in this section.
Many traits of agricultural importance in crop plants appear to be regulated by a large number of genes and therefore do not segregate into simple Mendelian ratios, as would be expected if only one or two genes were involved. Examples of such complex traits include height, branching, seed oil and protein yield and flowering time. During the past few years, however, the use of more sophisticated genetic tools has shown us that, although dozens of genes may be involved in the expression of such complex traits, much of the variation in their expression can be regulated by a small number of key genes. These regulatory genes can now be mapped using molecular markers and eventually isolated and sequenced. Research along similar lines in humans has revealed that some of the classical traits that were hitherto regarded as very complex, such as height, may be regulated by one or a few genes. For example, a gene called phog that is located on the human X-chromosome is reported to explain 70% of all height differences in children at the age...
