Heredity

Heredity is thought to have been discovered by Gregor Mendel in the 17th century. He is famous for cross breeding various types of pea plants based on the traits they exhibited. He used "true breeding" plants for each trait (short tall, yellow pod, green pod, wrinkled, smooth, etc). After crossing a tall plant with a short plant for example, the resultant generation (the F1 generation) would be 100% tall. This is becasue the tall phenotype is dominant to the short, or dwarf, phenotype. The F1 generation plants were allowed to self fertalize and creat the F2 generation. This is where the variation was seen and recorded. Mendel observed a 3:1 ratio of tall to dwarf respectively. It was not until later that punnett squares were created so Mendel had no model to explain this ratio. He repeated this experiment with several other traits always finding a 3:1 ratio. He concluded that each trait was controleld by a functional unit and was passed down from parent to offspring in an exact quantity. Mendel further realized that some traits must be dominant to others and only the dominant traits would be shown in the phenotype. Mendel cross-bred hundred of plants creating thousands of trials and he hand counted each phenotypic ratio.