The regulation of gene expression in DNA occurs in the highly compacted structure known as chromatin. Chromatin is composed of DNA wrapped around a histone octomer containing two copies of each the H2A, H2B, H3, and H4 histones. Any mutation of a specific histone, such as H2A, will alter the folding of chromatin and have an effect on the expression of genes in the cell, especially under conditions of stress such as cold shock. The yeast Saccharomyces cerevisiae, commonly used in fermentation and baking, is a powerful model organism in which to study responses to stress. Stress responses are highly conserved from yeast to humans, so understanding how yeast cells cope with cold shock and freezing will be relevant to our understanding of how many species cope with low temperatures. This project has two specific goals: To test the cold sensitivity of a collection of S. cerevisiae histone H2A mutants, and to measure the levels of expression of cold-inducible genes in the mutants that show cold sensitivity, in order to determine the different roles H2A mutations have in cold-shock gene expression.