DNA Structure and Replication: The Meselson-Stahl Experiment

Vocabulary terms covering DNA structure, historical base pair discoveries, the three proposed models of DNA replication, and the Meselson-Stahl experimental proof.

Double Helix

The structural form of DNA discovered in $1953$ by Watson and Crick, with help from Rosalind Franklin and Morris Wilkins, consisting of two strands that house $6,000,000,000$ base pairs.

Adenine, Thymine, Guanine, and Cytosine

The four specific DNA bases (A, T, G, C) that pair in a conserved manner (A with T, and G with C) to make up the $6,000,000,000$ base pairs of the genetic code.

Conservative Replication

A replication model hypothesizing that an original DNA molecule is copied to produce an entirely new second DNA molecule, which would yield one all-heavy and one all-light molecule after one cell division.

Dispersive Replication

A replication model proposing that a DNA molecule is cut into various parts, copied, and reattached, predicting that DNA would always contain a mixture of heavy and light material after multiple cell divisions.

Semi-Conservative Replication

The confirmed model of DNA replication where the two strands separate and each serves as a template to build a complementary strand, giving each daughter cell one old strand and one new strand.

Matthew Meselson and Franklin Stahl

The scientists who designed the experiment known as "the most beautiful experiment in biology," published in May $1958$ in the Proceedings of National Academy of Sciences, proving semi-conservative DNA replication in E. Coli.

Centrifugation

The experimental technique used to separate cellular components and DNA molecules according to their weight.

Polymerase Chain Reaction (PCR)

A widely used laboratory technique in forensics, paternity tests, and genetic testing that utilizes heat to separate DNA strands.