README MacTetrad an Excel spreadsheet designed for tetrad data for yeast genetics. One enters the genotypes of haploid spores into the spreadsheet and a Macro automatically classifies each tetrad as PD, NPD, or T for each pair of markers. The data is presented in a table, along with recombination distances. When one is performing a cross with multiple markers segregating, it is often difficult to identify the spores with a particular genotype. The spreadsheet macro makes this procedure simple. The macro also allows one to identify tetrads with a particular characteristic (i.e. tetrads that are NPD for two specific markers). This spreadsheet requires Excel (version 3.0 or 4.0) for the Macintosh. The spreadsheet also works with Excel for Windows running on an IBM PC, but we have not extensively tested it. For the Mac: The file MacTetrad69.hqx needs to be un-binhexed, and then it is a self-extracting Stuffit file. For the IBM: The file MCTTRD69.ZIP needs to be UNZIPed.