Aspects of genetic inheritance documented by Gregor Mendel. Mendelian genetics mainly refers to the ideas that (1) traits are influenced by discrete heritable elements (now known as genes) that come in different varieties (now known as alleles), (2) for a particular gene, each individual carries two alleles, one inherited from each parent, (3) during reproduction, one allele from each pair is randomly selected to be passed to the offspring and united with the other parent’s alleles, (4) because of these characteristics, trait ratios among offspring are predictable if the parental genotypes are known. For more details, see our historical essay on the topic.