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Mendel's Experiment (monohybridism) HTML5

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Gregor Mendel’s scientific work (1822-1884) and the publication of his discoveries (Experiments in Plant Hybridisation - 1865) mark the beginning of genetics (the study of heredity and genes). Using his now famous scientific approach, integrating a statistical tool, Mendel studied the transmission of traits in vegetable plants.  He chose the pea (pisum sativum) that satisfied all of his requirements. To understand the transmission of one characteristic from one generation to another, he artificially pollinated two varieties of peas from pure lineages. One with the "smooth seed" characteristic, the other with the "wrinkled seed" characteristic. The descendant (F1) only possessed smooth seeds.

He followed the experiment carrying out the autopollination of generation F1. What a surprise to see a constant proportion of the "wrinkled seed" characteristic in the F2 descendant.

From this experiment using millions of seeds, Mendel was able to confirm that:                    

  • It is not the characteristic that is transmitted during reproduction, but "factors" responsible for these characteristics.
  • Every organism inherits two of these "factors", one from each parent.
  • One "factor" can be dominant over the other which is recessive. The characteristic corresponding to this "factor" does not blend like the scientists of that time thought. It is expressed or is not expressed but there is no intermediate situation.

The word "factor" used above has been replaced by the word "gene" that was not discovered until the beginning of the XXth century.  Note that his publication did not have the expected impact during that time and he had to wait almost a half-century for it to be rediscovered.

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Learning goals

  • To illustrate the steps of Mendel's experiment (monohybridism).
  • To distinguish between Phenotype and Genotype: How the same phenotype can correspond to many genotypes.
  • To draw a conclusion between the results and the steps of Mendel's experiments, and the theory of genetics.
  • To understand the use of the Punnett square.