Mendel and his peas
How can we study inheritance?
The monk in the garden: Gregor Mendel
Research on heredity
- One form of a feature, such as tall, always concealed the other form, such as short, in the first generation after the cross. Mendel called the visible form the dominant trait and the hidden form the recessive trait.
- In the second generation, after plants were allowed to self-fertilize (pollinate themselves), the hidden form of the trait reappeared in a minority of the plants. Specifically, there were always about plants that showed the dominant trait (e.g., tall) for every plant that showed the recessive trait (e.g., short), making a ratio.
- Mendel also found that the features were inherited independently: one feature, such as plant height, did not influence inheritance of other features, such as flower color or seed shape.
- Characteristics such as flower color, plant height, and seed shape were controlled by pairs of heritable factors that came in different versions.
- One version of a factor (the dominant form) could mask the presence of another version (the recessive form).
- The two paired factors separated during gamete production, such that each gamete (sperm or egg) randomly received just one factor.
- The factors controlling different characteristics were inherited independently of one another.