Methods and compositions for identifying novel genes that share regions of homology with known genes from target groups of genes of interest are provided. The methods comprise systematically designing oligonucleotide primers that are specific for regions of homology within the nucleotide sequences of a target group of known genes and performing successive rounds of PCR amplification of nucleic acid material from an organism of interest. The PCR steps are intended to identify and amplify nucleic acids comprising both known and novel genes. Nucleic acid molecules comprising known genes are detected and eliminated from further consideration by dot blot analysis using oligonucleotide probes specific for the known genes in the target group. Potentially novel genes are subjected to further sequence analysis to confirm novelty and assayed for biological activity. Compositions of the present invention include novel polynucleotides, and variants and fragments thereof, that comprise novel genes and the polypeptides encoded thereby.