A difference between alleles that can be detected in DNA is called a polymorphism. Read Environmental Institute Lays Plans for Gene Hunt. Genes contain the information of a cell that is inherited by future cells. Each cell needs to copy its chromosome exactly and pass on an identical copy to each daughter cell. Experiments designed to demonstrate the genetic or environmental component of a trait generally aim to keep all components constant except the one tested.
Chance also determines the development of an organism.
None of this variation can be predicted from the genes, only from chance effects in development. Transfer of information between levels, by gene expression and development, and by genetic change. History of Genetics For thousands of years, humans have acted as agents of genetic selection, by breeding offspring with desired traits. Yet for most of this time, humans had no idea how traits were inherited. In 1866, Gregor Mendel discovered independent assortment of traits, dominant and recessive expression.