Hartwell, L. 1980. Mutants of Saccharomyces cerevisiae unresponsive to cell division control by polypeptide mating hormone. J. Cell Biol. 85: 811-822.

Questions for Thought

1) What was known at that time? What was the purpose of these experiments?

2) How did he make the mutants? Why test for mating ability at two temperatures? How many alleles of each gene? Are these genes the only ones required for mating? How do you know?

3) Complementation Tests:

b) Work through complementation tests (Fig. 1) and results in Table 1. Cryptopleurine causes loss of CRY+ chromosome and diploidization of cry- chromosome. Why did he need to select for cry sensitivity?

4) Table II: Why retest all the mutants for sterility? Why test different strains? What is he actually scoring? What is the phenotype? Why does some mating still occur?

5) Intrinsic v Extrinsic effects. Why do mixing experiments? What are possible outcomes? How would those be interpreted? Table III: What is evidence that defect is "cell autonomous"?

6) Morphology, agglutination, mating factor production/destruction, budding: What is the purpose of examining all these characteristics? How can one conclude that mutations affect "induction" of a process as opposed to some mechanisitic aspect of that process (e.g., induction of agglutinin production v sythesis or secretion of agglutinin itself)? What characteristics distinguish different genes? How do these differences suggest possible functions in pathway? Be specific.

7) Tables VIII, IX, Suppression by cdc28: What is the logic of the experiments with cdc28? What is the result and what does that tell you about the function of these genes in the pheromone pathway? in cell cycle control?