Reproduction is a defining criterion of biological life, and it requires that a parent transmit to its offspring a material carrier of the instructions for living — the **genetic material**. Nineteenth-century work established that this carrier resides in the nucleus: chemical isolation of nuclear contents showed them to comprise protein and an acidic substance named **nucleic acid**, while cytological observation of dividing cells showed that cytoplasmic organelles are partitioned haphazardly whereas nuclear chromosomes are apportioned with exact precision — an argument from fidelity of distribution to biological indispensability. This topic belongs to molecular biology and the history of genetics, and it frames the subsequent problem of the discipline: determining which of the two nuclear components, protein or nucleic acid, actually carries hereditary information.
Reproduction is a defining criterion of biological life, and it requires that a parent transmit to its offspring a material carrier of the instructions for living — the **genetic material**. Nineteen…