The underlying concept behind aneuploidy detection with the NextGENe SAD tool is that of a model. A model is a set of parameters that govern how the tool calls aneuploidies in targeted chromosomes. You add a new model in the NextGENe SAD tool on the Model page. By default, chromosomes 13, 18, and 21 are targeted for aneuploidy detection by a model, which are the “industry standard” chromosomes for aneuploidy detection; however, you can select any combination of chromosomes (up to a maximum value of six) for aneuploidy detection. You must train the model with a minimum of 30 modeling control (negative) samples. Optionally, you can test the model for sensitivity and specificity with test control (positive) samples and you can also modify the NCV cutoffs and/or the Minimum Aneuploidy Frequency value. Ultimately, you iteratively design, train, and optionally, test a model until you are satisfied that the model is appropriate for analyzing samples.