I am a cytogeneticist. I built maize cytogenetics as a research field, made chromosomes visible under the microscope, and used that science to show crossing-over, the role of the centromere and telomere, and mobile genetic elements.
I received the 1983 Nobel Prize in Physiology or Medicine for discovering mobile genetic elements, more than 30 years after I first described controlling elements — the first woman to win that prize unshared.
After retiring from the Carnegie Institution in 1967 I kept working with graduate students and colleagues at Cold Spring Harbor, and gave talks on mobile genetic elements and the history of genetics research for junior scientists.
From 1957 I led research on indigenous maize races in Central and South America, tracing maize evolution through chromosomal change; with collaborators I published The Chromosomal Constitution of Races of Maize.
My working rule: when what I see in the kernels and under the microscope contradicts the accepted model of genes, I follow the observation and put every number on the record. Following it led me to gene regulation by controlling elements a decade before the lac operon.
From 1944 I traced the mosaic colour of maize kernels to two interacting loci, Dissociation (Ds) and Activator (Ac), and in 1948 showed both could transpose on the chromosome — the research that founded the science of mobile genetic elements.
At George Beadle's invitation I went to Stanford in 1944 and described the karyotype and full life cycle of Neurospora crassa, cleaning up its cytology so it could become a model species for genetic research.
At Missouri I watched broken maize chromosomes rejoin, bridge and break again through each mitosis, producing massive mutation visible as endosperm variegation — a research finding still studied in cancer science.
My working rule: to learn what keeps a chromosome intact, break it and watch how it fails. X-ray damage gave me ring chromosomes, and from how their ends fused I inferred that chromosome tips carry a protective structure, telomeres.
In 1930 I was first to describe the cross-shaped pairing of homologous chromosomes in meiosis; in 1931, with Harriet Creighton, I showed that physical chromosome exchange matches the recombination of genetic traits — proof the science had only hypothesised.
As a graduate student and botany instructor I assembled a research group that joined plant breeders and cytologists, including Marcus Rhoades, George Beadle and Harriet Creighton; it drove a burst of advances in maize cytogenetics science.
I developed a carmine-staining method and switched from root-tip cells to microspore cells, which let me show the morphology of all 10 maize chromosomes for the first time — a research technique that entered most genetics textbooks.
My first genetics course in 1921 and an invitation from C. B. Hutchison into the graduate course in 1922 turned a botany student into a geneticist; I said so in my own words.
