The possible molecular genetic basis of the three mutant groups would be:
• 15% are lethal when they are knocked out: This means that they have essential gene function. Deoxyribonucleic acid (DNA) replication or protein synthesis is carried on with these enzymes. Mutations in these genes affect the protein synthesis and replication of DNA.
• 25% show some mutant phenotype with altered nutrition or altered morphology. These are auxotrophs. They are enzymes essential for amino acid synthesis and sugar metabolism. They are genes involved in the normal growth, metabolism and morphology or other characters.
• 60% are with no detectable mutant phenotype and resemble wild-type. These are redundant genes in which the pathways are not tested. They may be genes for ribosomal RNAs, histones, and tubulin. They are present in multiple copies. The yeast may require many genes during some situations seen only in nature. They may not be useful for testing under laboratory conditions.