A neomycin resistance cassette replaced 8kb of sequence that contains exons 3 through 6. The sequences encode three of the five amino acid motifs which are essential for guanine nucleotide binding to the alpha subunit. Western blot analysis did not detect any protein produced from this allele in extracts derived from spleen, thymus, lymph nodes or lungs of homozygous mutant mice. (J:59992)