Recessive epistasis in the
diploid Arginine biosynthesis pathway: trihybrid cross
& Tatum analyzed the genetics of Arginine
biosynthesis in the haploid bread mold Neurospora.
The same pathway occurs in diploid organisms:
genetic analysis of mutant alleles affecting metabolic
intermediates of Arginine production provides a
general model for the behavior of multiple gene loci in
a single pathway.
Homework: The Punnet
squares show the enzymatic [colour] and
growth [+ or -] phenotypes of a
cross between two trihybrid auxotrophic mutants
Assume dominance of the wild-type
allele at each locus (x+).
What general principles can be drawn from the patterns,
as related to dihybrid crosses, and other forms of gene
interactions in metabolic pathways?