Genetics is the scientific study of the structure, function, and transmission of genes in living things. The field of genetics includes many disciplines and uses many different techniques. Historically, genetic scientists (geneticists) investigated patterns of inheritance in whole organisms by observing the distribution and segregation of physical characteristics across several generations of breeding. This type of genetic research, called classical or Mendelian genetics, is still conducted today and remains invaluable for identifying and describing inheritance patterns and traits. The development of modern molecular biology and biochemistry has facilitated the growth of a different but complementary branch of genetic research, known as molecular genetics. This branch focuses on understanding the detailed molecular mechanisms that govern the transmission of genetic material from one generation to the next.

The observable characteristics that describe any organism (for example, height or eye color in humans, or flower size and color in plants) can...