Barbara McClintock and the discovery of jumping genes

Barbara McClintocks work on jumping genes
Source: Wikimedia Foundation (via Wikimedia Commons)
A review of McCintock's discoveries in genetics and the ongoing use of these findings in a study by researchers at the University of Michigan Medical school and U-M Centre for RNA Biomedicine

By Mili Jayadeep | Science Editor

Jumping genes may sound like a thing of fiction but thanks to the work of Barbara McClintock they are a well understood feature of genetics with far reaching implications for the scientific world.

Barbara McClintock was an American scientist with a love for science and learning from a very young age. Her father who was a physician supported and encouraged her in pursuing her interest. She became famous for her discovery of ‘jumping genes’, which were genetic elements in chromosomes that were mobile.

Genes found in DNA carry important genetic information that determines an organism’s characteristics. The human genome consists of 23 pairs of chromosomes which essentially is the blueprint of a human being. 

McClintock like many other female academics of her time experienced many challenges in her career, one of which was gaining recognition for her work at the time of her discovery. McClintock studied at Cornell university to achieve her degree qualifications and became the vice president of the genetics Society of America in 1939 and the president of the genetics society in 1944 owing to her publications and experimental research. However, when she returned to work as a professor at the university of Cornell where she studied, she came across another hurdle in her professional career. The university refused to hire a female professor and instead, she conducted research at Cornell funded by the Rockefeller Foundation. It was not until 1936 that she was hired by the University of Missouri. She later spent her time at the Spring Harbour Laboratory where she researched maize genetics.

McClintock’s dedication to her research resulted in advancements in this field. She revealed many ideas about genetics, which are invaluable to scientists today. For example, genetic recombination occurring during meiosis is a process by which crossing over of chromosomes in order to swap genetic information. Her focus was on maize genetics and was able to produce a genetic map and identified the chromosome region responsible for the subsequent physical traits. McClintock found that genetic information is transposable. When studying maize genetics, she identified the presence of what she referred to as “controlling genes” that were involved in the pigmentation of the crop. She discovered that these genetic elements were able to transpose to another area on the chromosome producing a new type of pigmentation or responsible for another physical characteristic. Unfortunately, she faced a large amount of criticism when she published her ideas, which were considered radical during that time.

Today, her work is recognised as being ahead of its time and it was not for years after her discovery that she received the necessary recognition for her contributions to genetic research. She became the first woman to receive a prestigious Nobel prize for Physiology and Medicine.

McClintock’s findings served as revolutionary in the field of genetics. Genetics is an area in science that is extremely complex with certain areas still not being fully understood. Scientists were only recently able to explain transposable elements and their influence on the regulation of genes. Researchers at the University of Michigan Medical school and members of the U-M Centre for RNA Biomedicine have contributed to the understanding of genetic evolution and helped uncover more about the role of transposable genetic elements in gene expression in a recent study published in the journal, Nature Communications

 The scientists conducted research on mouse and human cells to show the contribution made by these so-called ‘jumping genes’ in variation within a species and between different species. The study also revealed more about the behaviour of these transposable elements. They appear to also influence the way in which DNA interacts within its 3-dimensional environment affecting gene expression. In the field of genetics, in the early 1800s, scientists were only learning more about chromosomal shape. Then followed McClintock’s findings regarding jumping genes in maize that were responsible for different phenotypes in these plants which propelled research in this field. The focus of scientific interest in genetics then shifted to how these genes were being used in the organism. Adam Diehl, one of the new study’s authors says,

“It’s so exciting to be able to synthesize all this knowledge, and contribute to the next step of the story of species evolution.”

 The future of their work includes studying these transposable elements in a single population rather than between species. A new sequencing method will be used to unveil the variations between the transposable elements in human genes. This information could prove vital in understanding more about genetics and diseases as it has various applications such as genetic regulation in neurodegenerative diseases.

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