Gregor Mendel: Geneticist
Genetics is the study of heredity and variation in organisms. Genes are how this is accomplished. An Austrian monk, Gregor Mendel, developed the fundamental principles that would become the modern science of genetics. Mendel demonstrated that heritable properties are parceled out in discrete units, independently inherited. These eventually were termed genes.
Mendel reasoned an organism for genetic experiments should have:
1. a number of different traits that can be studied
2. plant should be self-fertilizing and have a flower structure that limits accidental contact
3. offspring of self-fertilized plants should be fully fertile.
Mendel's experimental organism was a common garden pea (Pisum sativum), which has a flower that lends itself to self-pollination. Most flowers allow cross-pollination, which can be difficult to deal with in genetic studies if the male parent plant is not known. Since pea plants are self-pollinators, the genetics of the parent can be more easily understood. Peas are also self-compatible, allowing self-fertilized embryos to develop as readily as out-fertilized embryos. Mendel tested all 34 varieties of peas available to him through seed dealers. The garden peas were planted and studied for eight years. Each character studied had two distinct forms, such as tall or short plant height, or smooth or wrinkled seeds. Mendel's experiments used some 28,000 pea plants.
Mendel finally settled on 7 characteristics to study; seed shape, seed color, flower color, pod shape, pod color, flower location, and stem height. Mendel's contribution was unique because of his methodical approach to a definite problem, use of clear-cut variables and application of mathematics (statistics) to the problem. Using pea plants and statistical methods, Mendel was able to demonstrate that traits were passed from each parent to their offspring through the inheritance of genes.
Mendel's work showed:
1. Each parent contributes one factor of each trait shown in offspring.
2. The two members of each pair of factors segregate from each other during gamete formation.
3. The blending theory of inheritance was discounted.
4. Males and females contribute equally to the traits in their offspring.
5. Acquired traits are not inherited.
| Introduction to Mendel | | Monohybrid Cross | | Dihybrid Cross | | Punnett Squares |
| Mendel's Conclusions |
©1998 William Jessee