Concept


Rather than looking at the pea plant as a whole, Mendel focused on seven individual traits that he could readily distinguish. He found that each trait has two alternate forms. For example, seed color can be green or yellow. He reasoned that each alternative form of a trait is specified by alternative forms of a gene. To follow the inheritance of genes from parent to child, Mendel first needed to be sure which genes each parent carried. Mendel developed "pure-bred" stocks by repeatedly breeding a plant to itself. This resulted in plants that showed only one form of alternative traits — and consistently passed only one gene alternate to offspring. Pure-bred plants with yellow seeds only produced offspring with yellow seeds. Pure-bred plants with green seeds only produced offspring with green seeds. Mendel reasoned that pure-bred plants must have two copies of the same gene.

Animation


Peas have distinctive traits that are inherited in predictable ways. Each visible trait is called a phenotype. Let me show you the traits I worked with. . . These are stem and flower traits. These are pod traits. These are seed traits. Here are the seven traits all together. Each trait has two phenotypes. Let's focus on one of these traits. I purchased pure-bred seeds for my experiments. Let me show you how these pure-breds were made. I allowed green and yellow pea plants to self fertilize for several generations. Pure-bred plants produce the same phenotype in all the offspring. I reasoned that pea color is controlled by one gene, which has a "green" form and a "yellow" form. Each form is called an allele. The pair of alleles is called the genotype.

Gallery


Gregor Mendel with fellow monks, around 1848.
Gregor Mendel and fellow monks, around 1862. Mendel is holding a fuschia sprig - a plant with which he made hybrids.
Mendel image referred to as the "handsome" Mendel, 1862.
Mendel and the teaching staff at the Brno modern school, 1864-65.
Cathedral that was the seat of the Augustinian order in Old Brno, 1873.
Mendel's garden plot at the Augustine monastery.
The colored pea flower.
Peas are a popular crop and many varieties existed for Mendel to work with. This is an illustration from Album Bernay (1876-93), and shows some of the pea traits Mendel used.

Audio/Video


Audio Glossary

Allele, Genotype, Phenotype

Video Interviews

Robert Olby

Professor of History Robert Olby teaches at the University of Pittsburgh, and has written several books on the history of genetics, including Origins of Mendelism and The Path to the Double Helix.

Clip 1 (0:50)
Mendel's personality & character: fighting a Monastary tax effectively ends his research career.

Clip 2 (0:35)
Mendel's personality & character: his inability to handle stress.

Clip 3 (0:20)
Mendel's personality & character: summary.

Biography


 

JOHANN GREGOR MENDEL (1822-1884)

The Man, the Monk

Johann Gregor Mendel was born in the Silesian village of Heinzendorf, now Hyncice in the Czech Republic. His parents were peasant farmers and very early on recognized their son's intellect. Mendel was able to stay in school and pursue an academic life. His sister, Theresia, actually sacrificed part of her dowry so that Mendel could get an education.

In 1843, Mendel entered the Augustinian Monastery in Brno (in what is now the Czech Republic) as a novice. In his autobiography, Mendel said that unlike other clerics, he didn't feel called to the Church: "my circumstances decided my vocational choice." Mendel did have a good life at the monastery; he was part of the cultural and scientific circles of the area. Also, the monastery sent him to school to continue his education.

Mendel had many interests, and while at the University of Vienna (1851-1853) he studied physics under Christian Doppler, and took courses in chemistry and zoology. As part of his monasterial duties, Mendel taught high school science at the local schools, and was remembered as a kind and good teacher.

The genetic experiments Mendel did with pea plants took him eight years (1856-1863). He published his results in 1865, and his laws of genetic inheritance earned him his place in history as the Father of Genetics.

Throughout the years, Mendel served the monastery loyally, and in 1868, Mendel became the Abbot, prelate of the Brno monastery. His responsibilities as prelate meant that Mendel had less time to spend on his scientific investigations. Mendel took his prelateship seriously; he was aware of the debt he owed to the monastery for supporting his scholarly interests. In the last decade of his life, Mendel became embroiled in a civic dispute about the taxes being levied on the monastery. The dispute caused ill-feeling between the monastery and the civic authorities and was not settled during Mendel's life.

There now exists in Brno a Mendel museum where his life is remembered.

Factoid

Links


 

Links

Mendel Web

This is a site where you can get a lot of information about Gregor Mendel, his life and scientific achievements. Read Mendel's descriptions of the pea traits he used in his experiments. You can also read an essay by Dr. Robert Olby, Mendel biographer, on how Mendel's work has been regarded since its rediscovery in 1900.

Electronic Scholarly Publishing

This site has the entire text for many classic genetics papers which can be downloaded and printed out in PDF format. Mendel's paper (1865) is one of the papers. To view and print these documents, you will need a copy of Adobe Acrobat Reader software, available without charge from Adobe Systems Incorporated.

The Mendel Museum

Check out this online exhibit for more on Gregor Mendel, based on a physical exhibit in Brno in the Czech Republic. Mendel spent most of his adult life in Brno at the Abbey of St. Thomas where he eventually became the Abbot.

Bibliography

  • Bowler, Peter J., 1989, The Mendelian Revolution, The Athlone Press, London.

  • Dunn, L. C., 1965, A Short History of Genetics, McGraw-Hill, Inc., New York.

  • Iltis, Hugo, 1932, Life of Mendel, W. W. Norton & Company, Inc., London.

  • Moore, John, A., 1985, Science as a Way of Knowing, American Society of Zoologists, Thousand Oaks.

  • Olby, Robert C., 1966, Origins of Mendelism, Constable and Company Ltd., London.

  • Orel, Vitezslav, 1996, Gregor Mendel, the First Geneticist, Oxford University Press, Oxford.

  • Portugal, Franklin H., and Cohen, Jack S., 1977, A Century of DNA: A History of the Structure and Function of the Genetic Substance, The Massachusetts Institute of Technology, Cambridge, Massachusetts.

  • Stern, Curt, and Sherwood, Eva, R., ed., 1966, The Origin of Genetics: A Mendel Source Book, W. H. Freeman and Company, San Francisco.

  • Stubbe, Hans, 1972 (English Translation), History of Genetics, The Massachusetts Institute of Technology, Cambridge, Massachusetts.

  • Sturtevant, A. H., 1965, A History of Genetics, Harper & Row, Publishers, New York.

Glossary


Allele - One of the variant forms of a gene at a particular locus, or location, on a chromosome. Different alleles produce variation in inherited characteristics such as hair color or blood type. In an individual, one form of the allele (the dominant one) may be expressed more than another form (the recessive one).
Genotype - The genetic identity of an individual, which may not show as outward characteristics.
Phenotype - The observable traits or characteristics of an organism, for example hair color, weight, or the presence or absence of a disease. Phenotypic traits are not necessarily genetic.

Children resemble their parents.
Genes don't blend.
Some genes are dominant.
Genetic inheritance follows rules.
Genes are real things.
All cells arise from pre-existing cells.
Sex cells have one set of chromosomes; body cells have two.
Specialized chromosomes determine gender.
Chromosomes carry genes.
Genes get shuffled when chromosomes exchange pieces.
Evolution begins with the inheritance of gene variation.
Mendelian laws apply to human beings.
Mendelian genetics cannot fully explain human health and behavior.
DNA and proteins are the molecules of the cell nucleus.
One gene makes one protein.
A gene is made of DNA.
Bacteria and viruses have DNA too.
The DNA molecule is shaped like a twisted ladder.
A half DNA ladder is a template for copying the whole.
RNA is an intermediary between DNA and protein.
DNA words are three letters long.
A gene is a discrete sequence of DNA nucleotides.
The RNA message is sometimes edited.
Some viruses store genetic information in RNA.
RNA was the first genetic molecule.
Mutations are changes in genetic information.
Some types of mutations are automatically repaired.
A chromosome is a package for DNA.
Higher cells incorporate an ancient chromosome.
Some DNA does not encode protein.
Some DNA can jump.
Genes can be turned on and off.
Genes can be moved between species.
DNA responds to signals from outside the cell.
Different genes are active in different kinds of cells.
Master genes control basic body plans.
Development balances cell growth and death.
A genome is an entire set of genes.
Living things share common genes.
DNA is only the starting point for understanding human biology.
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