Western Blotting is a semi-quantitative analysis of protein expression. This assay is applicable for most proteins and can be used to assess differences seen between diseased and wild-type mice. Western blots are used to determine if the agents (including cell, gene, or pharmacological based treatments) under study alter the levels of particular proteins in the tissue. Proteins are extracted from tissues and separated on the gel based on size. The gel is then transferred to a blot and by use of specific antibodies, unique proteins can be probed and quantitated.