Throughout her long and distinguished career, McClintock's work focused on the genetics of maize and, in particular, the relationship between plant reproduction and subsequent mutation. Beginning in the late s, she studied how genes in chromosomes could "move" during the breeding of maize plants.
She did groundbreaking research on this phenomenon, where she determined the physical correlate of genetic crossing-over. Later, during the s and s, McClintock showed how certain genes were responsible for turning on or off physical characteristics, such as the color of leaves or individual corn kernels.
She developed theories to explain the suppression or expression of genetic information from one generation of maize plants to the next that defied the common wisdom of molecular biology prevalent during the s. After encountering some skepticism about her research and its implications, she refrained from publishing her data in professional journals and only shared her research with a small circle of loyal colleagues.
In the early s, she traveled extensively, collected maize samples that demonstrated interesting evolutionary characteristics, and mentored junior scientists and young graduate students in maize genetics. McClintock and her colleagues spent two decades assembling data on differences in South American maize, which were finally published in as The Chromosomal Constitution of Races of Maize.
McClintock was recognized throughout her career as one of the most distinguished scientists of the 20th century. Restriction Enzymes. Genetic Mutation. Functions and Utility of Alu Jumping Genes. Transposons: The Jumping Genes. DNA Transcription. What is a Gene? Colinearity and Transcription Units. Copy Number Variation. Copy Number Variation and Genetic Disease. Copy Number Variation and Human Disease. Tandem Repeats and Morphological Variation. Chemical Structure of RNA.
Eukaryotic Genome Complexity. RNA Functions. Citation: Pray, L. Nature Education 1 1 Aa Aa Aa. Some of the most profound genetic discoveries have been made with the help of various model organisms that are favored by scientists for their widespread availability and ease of maintenance and proliferation. One such model is Zea mays maize , particularly those plants that produce variably colored kernels.
Because each kernel is an embryo produced from an individual fertilization , hundreds of offspring can be scored on a single ear, making maize an ideal organism for genetic analysis.
Indeed, maize proved to be the perfect organism for the study of transposable elements TEs , also known as "jumping genes ," which were discovered during the middle part of the twentieth century by American scientist Barbara McClintock.
McClintock's work was revolutionary in that it suggested that an organism's genome is not a stationary entity, but rather is subject to alteration and rearrangement-a concept that was met with criticism from the scientific community at the time.
However, the role of transposons eventually became widely appreciated, and McClintock was awarded the Nobel Prize in in recognition of this and her many other contributions to the field of genetics. McClintock and the Origins of Cytogenetics. Figure 1. Figure 2: Variation in kernel phenotypes is used to study transposon behavior.
Kernels on a maize ear show unstable phenotypes due to the interplay between a transposable element TE and a pigment gene. Plant transposable elements: where genetics meets genomics. Nature Reviews Genetics 3, All rights reserved. Expression of Ds in Maize. McClintock and the Theory of Epigenetics. Millions of Americans were unemployed. Male scientists were offered jobs.
But female geneticists were not much in demand. McClintock received two offers to travel and carry out research projects. She worked at several places, including Cornell and the University of Missouri in Columbia. Later, a group called the Guggenheim Foundation provided financial aid for her to study in Germany. McClintock went to Berlin, but returned to Cornell the following year.
Her skills and work were widely praised. But she still was unable to find a permanent job. They found that x-rays caused genes to change. Sometimes, the x-rays physically broke the chromosome. Genetic researchers looked for changes in the organism. Then they used this information to produce a map linking the changes to a single area of the chromosome. McClintock became interested in the way genes reacted to unusual events. She formed a successful working relationship with Lewis Stadler of the University of Missouri.
He had demonstrated the effects of x-rays on corn. Stadler sent maize treated with radiation to McClintock. She identified unusual areas she called ring chromosomes. She believed they were chromosomes broken by radiation. The broken ends sometimes joined together and formed a circle, or ring. This led her to believe that a structure at the end of the chromosome prevents chromosomes from changing. She called this structure the telomere. She became an assistant professor.
During her time at the university, she worked with plants treated with x-rays. For example, this is why kernels on the same piece of corn may have different colors. Here are a few more interesting tidbits you may not know about Barbara McClintock:.
However, Stern, like many other Jewish scientists, fled Germany amid the rise of Adolph Hitler and anti-semitism. She studied corn for 26 years.
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