APA Dictionary of Psychology

a type of inheritance that conforms to the basic principles developed around 1865 by Austrian monk Gregor Mendel (1822–1884), regarded as the founder of genetics. Mendelian inheritance is essentially determined by genes located on chromosomes, which are transmitted from both parents to their offspring. It includes autosomal dominant, autosomal recessive, and sex-linked inheritance. Mendel proposed two principles. The principle of segregation, or Mendel’s first law, states that recessive traits are neither modified nor lost in future generations as both dominant alleles and recessive alleles are independently transmitted and so are able to segregate independently during the formation of sex cells. The principle of independent assortment, or Mendel’s second law, states that there is no tendency for genes of one parent to stay together in future offspring.