15.2 What is DNA?
What is DNA and why is it useful in genealogy? DNA stands for deoxyribonucleic acid which is a “component of the cell that carries instructions for the development and operation of all living things.”1 Scientists did not always know the importance of nucleic acids. “DNA was isolated and discovered chemically before its functions became clear.… A series of experiments demonstrated that… the only chemicals that were consistently transmitted from one generation to the next were nucleic acids. As it became clear that DNA was the material that was transferred from one generation to the next, its functions began to be investigated.”2
Once the connection between nucleic acids and hereditary traits was proven, scientists began to understand there could be many important applications of understanding the structure and functions of nucleic acids.
“When its definitive role in heredity was established, understanding DNA’s structure became important.… The structure of DNA therefore, was elucidated in a step-wise manner through a series of experiments… [until it was clear that] a DNA molecule can look like a ladder, with a sugar phosphate backbone and nucleotide rungs. However, a DNA molecule forms a three-dimensional helical structure, with the bases tucked inside the double helix. Hydrogen bonding between nucleotides allows the intermolecular distance between two strands to remain fairly constant, with ten base pairs in every turn of the double helix.”3
“Nearly every cell in a multicellular organism possesses the full set of DNA required for that organism…. However, DNA does more than specify the structure and function of living things — it also serves as the primary unit of heredity in organisms of all types. In other words, whenever organisms reproduce, a portion of their DNA is passed along to their offspring. This transmission of all or part of an organism's DNA helps ensure a certain level of continuity from one generation to the next, while still allowing for slight changes that contribute to the diversity of life.”4
Because genealogy is “the study of the history of the past and present members of a family,”5 science that documents, tracks, and traces heredity may unlock important evidence that genealogists can use to prove or disprove biological connections between family members.