Retrospective on a century of genetics

The history of the International Congress of Genetics goes hand in hand with the history of genetics.

Since the inaugural congress in 1899, it has been held about every five years, with this year's event the 19th. Throughout the history of the congress, discoveries that have now become tenets of genetics have been highlighted, discussed and debated by the genetics community.

"There have been these landmarks through time," says the convener of the 19th congress, Prof Phil Batterham of the genetics discoveries that have underpinned the event. Many of them, he notes, are now taken for granted, like Thomas Hunt Morgan's proposal that genes were located on chromosomes.

he first International Congress of Genetics was a plant breeding conference, organised by Britain's Royal Horticultural Society to focus on the emerging science of hybridisation and cross-breeding. At the conference, William Bateson, considered by many to be the founding father of 20th century genetics, called for a new research emphasis on the study of discontinuous variation, and the use of hybridisation and cross-breeding as a tool to study variation.

A year later, in 1900, Mendel's rules were 'rediscovered' after languishing in obscurity since 1865, kicking off the first century of the new science. According to Robert Haynes, in a paper summarising the early history of genetics and the genetics conference (published in Genetics in 1998), Bateson became Mendel's champion and in 1905 came up with the term 'genetics' to describe the new science. Other terms Bateson introduced to the new field of study include allele, homozygous and heterozygous.

As the president of the third congress in 1906, Bateson was also instrumental in changing the name of the conference to the International Conference of Genetics (later changed to International Congress), and retrospectively renaming the previous two events as the first and second conferences.

Over the next half a century before Watson and Crick determined the structure of DNA, a number of landmark discoveries were made. Thomas Hunt Morgan proposed a theory of sex-linked inheritance for the first mutation discovered in the fruit fly Drosophila melanogaster, a year before the fourth Congress, and followed it up in 1915 with the development of the gene theory and the principle of linkage, suggesting that genes were linearly arranged on chromosomes. In the process, he established Drosophila as one of the key model organisms for the study of genetics. Subsequently other models were also developed for mapping of chromosomes, notably maize and silkworms.

In 1927, at the 5th International Congress in Berlin, Hermann Muller gave the first report on his discovery of X-ray mutagenesis. The big breakthrough here was the recognition that mutations could be produced "to order" allowing genetic maps to be created which could then be used to analyse the chromosomal aberrations caused by the mutagenesis.

By 1939's 7th International Congress, several papers were presented that linked UV-induced mutagenesis to the UV absorption spectrum for DNA, but they weren't enough to convince scientists that DNA was the genetic material in chromosomes. Nucleic acids had been discovered in the 1920s to be the major component of chromosomes and in the 1930s the four-base composition was described as a tetranucleotide with purely structural or physiological roles.

But chemical mutagenesis was not announced until after the Second World War, at the 1948 8th International Congress. Charlotte Auerbach presented a paper describing her discovery, previously classified as a wartime secret, of the mutagenicity of mustard gas. Chemical mutagenesis continued to be a hot topic at the next congress, held in 1953.

At around the same time, experimental genetics was shifting from cytogenetics and mutagenesis to the study of microorganisms, including the bacterium Escherichia coli and bacteriophage or bacteria-infecting viruses. In 1944, Oswald Avery demonstrated that DNA was the heritable agent and in 1946 Joshua Lederberg discovered recombination in bacteria. Around the same time, the link between genes and enzymes was discovered. And in 1953, of course, James Watson and Francis Crick came up with the structure of DNA.

According to James Crow, in his introductory speech (which was actually given at the end of the conference) at the 18th International Congress of Genetics on genetics in the 20th century, the first 50 years of genetics focused on using phenotypes to try to understand genotypes, while the second 50 years has focused on using the genotype to try to understand phenotypes.

Crow noted that following Watson and Crick's discovery, the role of RNA was clarified, and the processes of transcription from DNA to RNA, followed by translation into proteins using the genetic code were worked out. And Crow also pointed out that where the techniques available to early researchers were few, the last 50 years have been characterised by an astonishing cascade of powerful new techniques. Some of these, like DNA sequencing technology and the polymerase chain reaction, have almost single-handedly driven genetics forward.

As one of the greatest achievements in human genetics, the Human Genome Project, which Crow noted appeared to be an almost unattainable endpoint in genetics in 1950, has produced a working draft of the genome, and sometime this year the finished sequence is scheduled to be published.

According to Batterham, this year's congress will focus on the linkage between the genome and life, providing a focus for the event that is perhaps stronger than previous years.

"We know a lot about individual genes, but not a lot about genomes, how the genes function together," he says. "But the level of complexity we can now analyse is much greater."

Australian Biotechnology News is a major sponsor of the IX International Congress of Genetics. For more information, see www.geneticscongress2003.com