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  • Mendels Investigations

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  • Chapter 1. Mendels Investigations

    CHAPTER 1 Mendels Investigations

    Lesson Objectives

    Explain why and how Mendel studied pea plants. Describe the results of Mendels experiments. State Mendels laws of segregation and independent assortment. Outline the genetics of inheritance.


    allele dominant allele genetics genotype heterozygote homozygote hybrid law of independent assortment law of segregation locus phenotype pollen pollination recessive allele


    People have long known that the characteristics of living things are similar in parents and their offspring. Whether itsthe flower color in pea plants or nose shape in people, it is obvious that offspring resemble their parents. However, itwasnt until the experiments of Gregor Mendel that scientists understood how characteristics are inherited. Mendelsdiscoveries formed the basis of genetics, the science of heredity. Thats why Mendel is often called the father ofgenetics. Its not common for a single researcher to have such an important impact on science. The importance ofMendels work was due to three things: a curious mind, sound scientific methods, and good luck. Youll see whywhen you read about Mendels experiments.

    An introduction to heredity can be seen at (17:27).




    MEDIAClick image to the left or use the URL below.URL:

    Mendel and His Pea Plants

    Gregor Mendel was born in 1822 and grew up on his parents farm in Austria. He did well in school and becamea monk. He also went to the University of Vienna, where he studied science and math. His professors encouragedhim to learn science through experimentation and to use math to make sense of his results. Mendel is best knownfor his experiments with the pea plant Pisum sativum (see Figure 1.1). You can watch a video about Mendel and hisresearch at the following link: .

    FIGURE 1.1Gregor Mendel. The Austrian monk Gregor Mendel experimented withpea plants. He did all of his research in the garden of the monasterywhere he lived.

    Blending Theory of Inheritance

    During Mendels time, the blending theory of inheritance was popular. This is the theory that offspring have a blend,or mix, of the characteristics of their parents. Mendel noticed plants in his own garden that werent a blend of theparents. For example, a tall plant and a short plant had offspring that were either tall or short but not medium inheight. Observations such as these led Mendel to question the blending theory. He wondered if there was a differentunderlying principle that could explain how characteristics are inherited. He decided to experiment with pea plantsto find out. In fact, Mendel experimented with almost 30,000 pea plants over the next several years! At the followinglink, you can watch an animation in which Mendel explains how he arrived at his decision to study inheritance inpea plants: .

    Why Study Pea Plants?

    Why did Mendel choose common, garden-variety pea plants for his experiments? Pea plants are a good choicebecause they are fast growing and easy to raise. They also have several visible characteristics that may vary. These