The names of the majority of families have tradition- ally been based on a genus within the family and have names ending in -aceae, such as Rosaceae, based on Rosa. However, there are a number of families that have not traditionally conformed to this pattern. While it is perfectly acceptable to continue to use these nonconforming names, the modern trend is to use names with -aceae endings. These families are as follows, with the more modern name in parentheses: Compositae (Asteraceae), Cruciferae (Brassicaceae), Gramineae (Poaceae), Guttiferae (Clusiaceae), Labiatae (Lamiaceae), Leguminosae (either Fabaceae or split into three families based on previous subfamilies: Caesalpiniaceae, Mimosaceae, and Papilionaceae), Palmae (Arecaceae), and Umbelliferae (Apiaceae). Rosa chinensis
“Semperflorens,” old crimson china rose
Cydonia oblonga, quince
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B
arbara McClintock, born Eleanor McClintock in Hartford, Connecticut, was an American scientist who became one of the world’s most distinguished cytogeneticists, studying the genetics of maize.She developed her passion for information and science during high school and went on to study botany at Cornell University’s College of Agriculture. An interest in genetics and the new field of cytology— the study of cell structure, function, and chemistry— led her to take the graduate genetics course at Cornell. And so began her life-long career in the development of maize cytogenetics and the study of the structure and function of the cell, especially the chromosomes.
She soon became recognized for her aptitude for, and thorough approach to, the subject. In her second year of graduate work, she improved on a method that her supervisor was using and she was able to identify maize chromosomes. It was a problem he had been working on for years!
In her groundbreaking cytogenetic work, Barbara studied maize chromosomes and how they change
during the reproduction process. She developed the technique for visualizing the maize chromosomes and, using microscopic analysis, demonstrated many fundamental genetic processes during reproduction, including genetic recombination and how chromo- somes exchange genetic information.
She produced the first genetic map for maize, demonstrating that particular chromosome regions were responsible for creating a particular physical characteristic, and she demonstrated how the recombination of chromosomes correlated with new characteristics. Until this time, the theory that genetic recombination could happen during meiosis (see p. 88) was just that—a theory. She also showed how genes are responsible for turning physical characteristics on or off, and developed theories to explain the repression or expression of genetic information from one generation of maize to the next.
Unfortunately, Barbara was often thought of as being too independent and a bit of a “maverick,” not in keeping with most scientific institutes’ ideas of a “lady scientist.” As a result, she spent many years moving from institute to institute, especially between Cornell and the University of Missouri. She even spent some time working in Germany. Because her work on gene regulation was conceptually difficult to understand, it was not always accepted by her contemporaries. She often described the reception of her research as “puzzlement, even hostility.” However, she was never deterred from continuing.
In 1936, she was finally offered a faculty position at the University of Missouri and was Assistant Professor for five years until she realized that she would never be promoted. She left and worked for a summer at the Cold Spring Harbor Laboratory, finally accepting a
B a r b a r a M c c l i n t o c k
1 9 0 2 – 1 9 9 2
Barbara McClintock was one of the world’s most distinguished cytogeneticists, renowned for her thorough approach and research.
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Zea mays, corn, maize
Dr Barbara McClintock determined that the variations in corn color were due to specific genetic elements.
full-time position the following year. It was at Cold Spring Harbor that McClintock figured out the process of gene expression in maize chromosomes.
For this and her other work, Barbara was awarded the Nobel Prize for Physiology or Medicine, the first woman to win the prize unshared. The Nobel Foundation credited her with discovering mobile genetic elements and she was compared to Gregor Mendel by the Swedish Academy of Sciences.
In 1944 she undertook the cytogenetic analysis of Neurospora crassa, a type of bread mold, at Stanford University. She successfully described this species’ number of chromosomes and its entire lifecycle. N. crassa has since become a model species for classical genetic analysis.
Because of her work with maize genetics, in 1957 she started research on the indigenous strains of maize found in Central and South America. She studied the evolution of maize races and how chromosomal changes had affected morphological and evolutionary characteristics in the plants. As a result of this study, Barbara and her colleagues published The Chromo- somal Constitution of Races of Maize, which played a large part in the understanding of the ethnobotany, paleobotany, and evolutionary biology of maize.
Apart from the Nobel Prize, Barbara received numerous honors and recognition for her ground- breaking work, including being elected as a member of the National Academy of Sciences—only the third woman to be elected. She received the Kimber Genetics Award, the National Medal of Science, the Benjamin Franklin Medal for Distinguished Achievement in the Sciences, and was elected a Foreign Member of Britain’s Royal Society. She was also the first female President of the Genetics Society of America. A small selection of some of the various corn mosaic color variations that Barbara McClintock discovered were the result of chemicals inhibiting the synthesis of color pigments.
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B O T A N y F O R G A R D E N E R S