Abstract: A method for determining the nucleotide sequence of a chromosome. The chromosome is hydrolyzed to form a mixture of oligonucleotides having unknown nucleotide sequences. The mixture is exposed to a library of oligonucleotide probe pairs having known sequences. The probe pairs are located so that they hybridize to outer opposed sections of the chromosomal oligonucleotides. The use of oligonucleotide probe pairs provides for sequencing of relatively long unknown DNA sequences using relatively short oligonucleotide probes.

Abstract: A stripper seal protection and operating tool sealing element and method for protecting stripper seals during drilling operations with operating tools having both polygonal and circular cross sections. The stripper seal protection and operating tool sealing element includes a lower protective sleeve for expanding the stripper seal radially outward to prevent contact with polygonal operating tools and includes a head portion integral therewith for mounting an elastic sealing ring for packing off on the polygonal operating tool. The protective sealing element is particularly useful for applications in diverter housings of the rotating insert type. The protective and sealing element is inserted and removed from the diverter coupling concurrently with polygonal operating tools such as kellies. The protective sealing element also includes rotating lock means to provide common rotation of the rotating insert with the kelly.