Practice question

Neurospora crassa red bread mold offered unique advantages: haploid vegetative mycelium exposing recessive mutations immediately without dominance masking, simple nutritional needs allowing prototrophic growth on minimal medium containing sucrose, mineral salts and biotin, and rapid sexual cycle permitting crosses and tetrad analysis. Beadle and Tatum exploited these features by irradiating conidia, culturing on complete medium then testing failure on minimal medium. Auxotrophs requiring arginine, nicotinamide or pyridoxine mapped blocks to single enzymes, demonstrating direct link between gene and biochemical step, impossible with diploid pea.