[Encyclios]

The twentieth century

From the early twentieth century onward it was a succession of discoveries and formulations of theories. K. E. Correns and T. Boveri in 1902, W. S. Sutton in 1903 pointed out the close parallelism between the behavior of chromosomes in gametogenesis and fertilization and the trend of Mendelian characters from one generation to the next. They thus came to formulate the “chromosomal theory of inheritance,” according to which the genes carrying inherited characters are located in chromosomes and transmitted with them, through gametes, from one generation to the next. Subsequently, other important discoveries were those made by T. H. Morgan and his students.

Morgani discovered sex chromosomes, correctly interpreted sex-linked inheritance and formulated the concept of linkage (association) and crossing-over (exchange) of genes. Other discoveries followed, but perhaps the most resounding came in 1953, when J. D. Watson, F. H. Crick and M. Wilkins elucidated the structure of the nucleic acid molecule. The code by which information is recorded in DNA molecules was discovered by M. W. Nirenberg and S. Ochoa. Thus, the analysis of genetics has truly reached the basis of life phenomena and it is now possible to study how genes function and how they are expressed.

The fields of application of genetics are the most varied, from medical to chemical, pharmaceutical, industrial, agricultural and animal husbandry. Of long-standing tradition and experience is the obtaining in animal husbandry and agriculture of animal (transgenic animals) and plant (GMO, genetically modified organisms, obtained by genetic manipulation) varieties endowed with particular requirements and well adapted to breeding and production in particular environments (for example, the obtaining of short-legged cattle that less easily can escape from pens and that of numerous varieties of wheat each adapted to cultivation in particular places). Even more numerous are the research fields of genetics, three in particular have had very extensive developments: bacterial genetics, population genetics, and gene genetics.