Concept


While, on the whole, offspring appear to be a mixture of parental characteristics, Mendel showed that genes for individual traits do not blend. Instead, genes are maintained as discrete bits of hereditary information — unchanged through generations. Mendel proposed that genes behave like atoms that compose a pure substance — they can combine in various ways, but always maintain their distinct identities. For example, one might expect that a cross between green-seeded and yellow-seeded plants produces offspring with seeds of a green/yellow blend. However, Mendel found that this cross produces only offspring that show one or the other of the parental colors. No intermediate blends are seen.

Animation


I showed that traits inherited from parents do not blend... ...but they are inherited as discrete bits of information, unchanged through generations. I then had to figure out why only one trait was seen in the offspring of the pure-bred crosses.

Gallery


Mendel with group from Vienna before the Grand Hotel in Paris en route to London, 1862. Mendel was not scientifically isolated. He traveled and was in contact with other scientists.
First page of Mendel's paper (German), Experiments in Plant Hybridization, in his handwriting, 1865.
Mendel's notes on some of his pea plant results in his handwriting.
Written on the leaf is "fouleben," which means "evenly" in German.
Mendel designed and built these hives to do his bee breeding experiments.
Mendel's drawings of sunspot activity from two pages of his meteorological notebooks.

Audio/Video


Audio Glossary

Allele, Gene

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 (0:30)
Was Mendel "well connected" in the scientific community?

Biography


 

JOHANN GREGOR MENDEL (1822-1884)

The Scientist

Gregor Mendel is known for his work on the laws of inheritance. However, he did more than just grow pea plants.

Gregor Mendel had an enquiring mind. At the University of Vienna, he took as many science courses as he could. It was probably Mendel's exposure to physics under the tutelage of Christian Doppler that gave the mathematical context for his later experiments. Despite his responsibilities and his ever-increasing workload as prelate of the monastery, Gregor Mendel always found time for scientific investigations.

Mendel tried to make practical use of what he found from his pea breeding experiments. He was a beekeeper; he designed beehives, and was working on breeding a strain of bees with improved honey production.

Mendel was a noted meteorologist, a founding member of the Austrian meteorological society. Mendel kept daily logs of weather patterns, and did a careful analysis of the tornado that struck Brno in 1870. Mendel also kept track of sunspot activity in relation to "northern lights" (aurora borealis) and disturbances in telegraph communication.

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 what Mendel says about the 7 non-blending pea traits. Also read Dr. Margaret Peaslee's essay on her recent travels to Brno and the Mendel museum.

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.

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).
Gene - The functional and physical unit of heredity passed from parent to offpsring. Genes are pieces of DNA, and most genes contain the information for making a specific protein.

Children resemble their parents.
Genes come in pairs.
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.
adi_at_dnaftb