This lesson has two parts, Mendelian Genetics and Characteristics that Vary Continuously. Part I. Mendelian Genetics Background Information 1. Living things naturally exist in communities composed of some similar and some different kinds of organisms. Within populations of similar organisms, we see variations of certain traits expressed. Many traits are produced by a single gene.
Genes are units of inheritance.
Single gene traits are called Mendelian traits because they follow the simple inheritance patterns first described by Gregor Mendel . In the 1850s, Mendel made hybrids between different varieties of pea plants and kept careful track of the traits displayed by the offspring. Mendel discovered that traits of the parent plants were passed on to the progeny plants in reproducible patterns. In humans, some Mendelian traits include hair curliness and hair color. Other traits, such as skin color and weight are affected by multiple genes.