A new and potentially reliable method for the isolation of yeast artif
icial chromosome (YAC)-insert termini, termed junction trapping, is de
scribed. This method is based on simple partial digestions of the YAC-
containing yeast strain, ligation to a plasmid vector, and selection o
f the termini by two rounds of polymerase chain reaction (PCR). To dat
e, the method has generated both terminal sequences from each of nine
YACs (100%) that have been examined.