When diploid S. cerevisiae cells undergo meiosis, four haploid spores are produced which are enclosed within a sac called an ascus. Using a micromanipulator, the 4 spores (the "tetrad") can be "dissected" out of the ascus and separated on an agar plate. The spores then germinate, and the colonies that arise can be tested for the presence or absence of phenotypes characteristic of the genetic markers present in the original diploid strain. In this way the segregation pattern of the genetic markers can be assessed, allowing determination of genetic linkage of, and distances between, the markers. When 2 genetic markers are analyzed in this way, the data is called 2_point_data.

This definition is in context to Yeast Genome. See more contextual defintions for Tetrad Analysis.