This project carries out the pilot CRISPR/Cas9 screens in the K562 background. Its goals are to confirm that positive controls work, and to assess the effects of experimental parameters (listed below) on the sequencing-based fitness readout. We test 1) length of selection 2) biological replicates 3) sampling variation during bottlenecks 4) sampling variation during DNA preparation 5) sequencing depth to inform the setup for the next round of experiments. To do so, we propose to sequence 13 samples (6 timepoints, 2 biological replicates, 2 severe bottlenecks during growth, 2 bottlenecks during DNA preparation, and the screening library itself) on two lanes of HiSeq, using 19bp reads. The sequencing libraries are prepared in our lab. This data is part of a pre-publication release. For information on the proper use of pre-publication data shared by the Wellcome Trust Sanger Institute (including details of any publication moratoria), please see http://www.sanger.ac.uk/datasharing/