Gene structure of gna1 , deletion cassette and construct for transformation with the gna1 Q204L allele. (a) The gene structure of gna1 is shown along with its exons and introns and the predicted GNA1 protein. (b) Construction of a transformation cassette for deletion of gna1 by replacing its open reading frame with the pyr4 gene as a selection marker. (c) Strategy for mutational activation of GNA1 by construction of a transformation cassette comprising a single amino acid exchange at position 204 as indicated by a triangle. The restriction sites SalI and ApaI have been introduced using nested primers to facilitate cloning.