On October 2, 2021, current and former colleagues at the Department of Molecular Biology (and departments that have merged with them) congratulate Professor Emeritus Marianne Rasmuson on her 100th birthday. Professor Rasmuson is still active in her field, which is genetics. She was appointed professor at the current Faculty of Science and Technology in 1979 and she has been a member of the Royal Swedish Academy of Sciences since 1980. Professor Rasmuson is a fantastic role model for us as subject specialists. She has proved that it is possible to remain curious and keep one’s interest in a scientific field alive throughout a long life, and to keep contributing new knowledge and insights to society, even after one’s formal employment has ended. As an example of this, we now have the opportunity to enjoy a new essay on the history of genetics. We wish Marianne a particularly happy birthday and continued good health.
Genetics: a hundred years of inheritance research, by Professor Marianne Rasmuson
The study of heredity began in earnest the year 1900 with the rediscovery of Mendel’s laws. The name genetics came from the factors that were presumed to be responsible for heredity, these soon came to be called genes. However, the actual gene long remained an abstract factor. The study of genetics grew and branched out during the first half of the century. Intricate crossings and detailed studies of variants that could be observed in the offspring of model organisms, such as Drosophila and corn, were the road to new discoveries.
Today, molecular methods and technological progress has changed the lines of research. The gene materialized as a sequence in the DNA’s double helix with a known structure and function, that could be copied, moved, and modified. Progress has been impressive, but the insights that were accumulated before molecular biology and computers stepped onto the stage have not been meaningless. During the long period of time I have been granted to follow the development of this field, I have thought about the paths the research has embarked upon. I would like to highlight three areas that were initiated early and later developed to completely new dimensions.
Quantitative traits: from single- to multiple gene inheritance
The early geneticists chose to study clear and distinct varieties in plants and animals, of which Mendel’s smooth or wrinkled peas and the eye color of the fruit fly were early examples. However, much of the variation within one species is of another kind, a moving transition from minimum to maximum in regards to size, amounts, or intensity. It was obvious at an early stage that mendelian genes could cause variation of this kind but that the situation is further complicated by a large and unknown number of synergetic genes and environmental effects. Special statistical methods, such as the analysis of variance, were required to allocate the variation of different components. If correctly analyzed, the meaning of genetic factors can be separated from environmental influence and be divided according to their own traits. The total influence of heredity, or heritability, is crucial within plant- and animal breeding and it has increased our understanding of the tremendous number of genes that influence variation. In the fields of medicine and the behavioral sciences, hundreds of thousands of DNA variants have been tested in thousands of individuals to find sequences that are of importance for body length, intelligence, and complex diseases such as cancer, autism, and schizophrenia.
The principles behind the distribution of genes and genotypes in a population with free propagation was first approached in a purely theoretically manner. The effect of different types of influence, such as selection, inbreeding, mutation, and number of individuals was determined in mathematical terminology at an early stage but could not be confirmed in nature due to a lack of distinctively varying traits. This was first rectified after molecular methods revealed a plentitude of hidden variations in all types of different organisms, and, as a result, new opportunities were discovered that enabled the analysis of the allocation of biological variation within species and how populations can adapt by receiving mutants and exchange genes. The spread of humanity across the globe is reflected in the gene frequencies of current populations. When this data is complemented with DNA-studies of our ancestors, all the way back to the Neanderthals, it is possible to catch a glimpse of our origin.
Mutations and the genetic clock
Mutations, random changes in the genes, were observed early on and their emergence became the subject of a lot of speculation. Despite the fact that most of the studied mutations impaired the vitality of life, it was clear that there must also be useful and completely indifferent or neutral changes. Theoretical studies of the continued life of neutral mutations showed a certain probability that such a mutation might eliminate earlier alleles and be fixed in the genome. In an evolutionary time-scale, the branches of a family tree should gather their own variants, more the longer they have been separated. It is possible to predict the time for such transfers, which provides an opportunity to predict evolutionary processes. Since the tendency to mutate vary between different genes, it is possible to use genes with slow or fast mutation rates in different timescales, from the organisms branching early to more recent genealogy.
Today, many of the old research questions have lost their timeliness. But with hindsight, many of the speculations have been confirmed. Researchers have become dependent on expensive technologies which has incentivized teamwork and presentations of results now always include a large number of co-authors. In this manner, genetics has been able to conquer new domains. However, as always before, progress depend on a combination of new perspectives, critical trials, and industrious work. Precisely where this might lead in the future is just as difficult for us to predict as it would have been for the pioneers of the past to predict where research is today.