- Basic Concepts
- DNA & RNA
- Simple Inheritance
- Modify Mendelian Ratios
For thousands of years (or more!), humans have known that progeny resemble their parents and have taken advantage of this knowledge to try to breed better plants and animals. However, the basic mechanism by which traits are inherited was not understood until 1866, when a Moravian monk named Gregor Mendel published his "Experiments on Plant Hybridization." This paper described the inheritance of simple traits such as seed color and plant height in peas and provided the foundation for the entire modern-day study of genetics.
So what made this paper so special? Many other scientists had studied plant hybridization in the past. In fact, Mendel gained many insights from their experiments. However, Mendel's studies provided the first evidence that traits were passed on from parents to progeny as pairs of discrete factors that remained unchanged from generation to generation. In other words, Mendel was the first scientist to publish the evidence that genes existed.
Mendel also described how these factors separated during meiosis (the concepts of segregation and independent assortment) and how a phenotype could disappear in one generation, only to reappear in the next (the concept of dominance). These concepts are described in more detail in later sections of this web site.
We now know that the inheritance of traits, while based on the concepts that Mendel described, is a much more complicated story than he envisioned. In fact, we are still learning about the genetic mechanisms that underlie many complex traits. Thus, this web site will not only introduce you to the concepts that Mendel developed but will also describe and demonstrate those more complex systems that Mendel never saw in his pea garden.