The gamma-subunit of mouse 7S nerve growth factor (gamma-NGF) is a member of a family of closely related serine proteases that includes kallikreins and tamases. We have isolated from a DBA/2J male submaxillary gland cDNA library a clone, pSM676, which codes for gamma-NGF. Sequence analysis of the clone shows that it codes for the C-terminal 138 amino acids of the protein plus 23 bases of the 3'-nontranslated portion of the message. The predicted amino acid sequence agrees with that determined by Thomas et al. (1) for the gamma-subunit of nerve growth factor from Swiss Webster mice except for the single, conservative substitution of glutamate for aspartate at amino acid 175. When used as a probe for Southern blot analysis, pSM676 hybridizes to at least twelve fragments of restricted mouse genomic DNA which correspond to several different serine protease genes. Using mouse-hamster hybrid cell lines and recombinant inbred strains of mice, we have demonstrated that all of the genes which show homology to pSM676 are located on mouse chromosome 7, clustered at or near the Tam-1 locus.

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Spontaneous secondary mutations of the ochre suppressor SUP6 were selected in a haploid strain of Saccharomyces cerevisiae. Unselected tetrads were dissected from crosses heterozygous for one of three alleles of SUP6 and for three other loci in this region which span a length of 14 map units (his2, cdc14 and met10). The study showed that all of these markers were characterized by high frequency of meiotic gene conversion and long conversion lengths which frequently extended into adjacent marked loci. Despite the high conversion frequency of SUP6, recombination between alleles of this locus reached a maximum frequency of only 2 × 10-3 prototrophs/spore. Although the allelic recombination frequencies were not distance dependent and consequently could not be used to order the alleles, the inequality between the two recombinant outside marker combinations among selected intragenic recombinants produced an internally consistent map of the suppressor locus. Recombination at SUP6 (whether detected as conversion in tetrads or the production of recombinants among random spores) was accompanied by significantly less than 50% outside marker recombination.

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