MONITORING THE EFFICACY OF HYBRID SELECTION DURING POSITIONAL CLONING- THE SEARCH FOR BRCA1

Positional cloning often requires isolation of candidate genes from a large, genetically defined region. Hybrid selection (direct cDNA selec tion, solution hybrid capture) is a rapid, simple procedure that has b een used to identify expressed sequence tags (ESTs) from cloned genomi c DNA. We used hybrid selection to screen a 600-kb region that include s the BRCA1 gene. From a set of 931 sequenced clones, we obtained 118 nonoverlapping candidate ESTs from ovary and lymphocyte cDNA. We analy zed the results of our hybrid selection experiments with particular at tention to the overall completeness, efficiency, and background noise of the experiment. We introduce simple parameters that serve as measur es of important aspects of the hybrid selection process in the context of positional cloning.