Among Delta-back stripped fish, there are two genes that segregate independently of one another. Suppose the alleles at the first locus are A (dominant) and a (recessive) and the alleles at the second locus are B (dominant) and b recessive). If an AABB fish mates with an aabb fish, and their offspring are inter-crossed, the proportion of F2 fish that show a recessive phenotype at the first locus and a dominant phenotype at the second is: