This project is focused on our continuing efforts to improve the speed, accuracy and efficiency of genotyping for large-scale gene mapping studies. During the past year we have evaluated several alternative molecular marker sets for screening the entire human genome, including a newly available set of microsatellite markers based primarily on dinucleotide versus tetranucleotide repeats. Our collaboration with the NHGRI has provided us with access to their extensive experience in developing another marker set, including the method known as pig-tailing which has been shown to substantially reduce artifacts associated with this method of marker genotyping. Additional efforts have been focused on incorporating our new instruments into these analyses including DNA sequencers and a robotic laboratory workstation.