GENE 500 Study Guide - Midterm Guide: Synthetic Lethality, Wild Type, Meiosis
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In this case, the observed phenotype of the double mutant provides information about the order in which the proteins act and whether they are positive or negative regulators. A suppressor mutation is a second mutation that restores fu(cid:374)(cid:272)tio(cid:374) loss (cid:272)aused (cid:271)y a rst (cid:373)utatio(cid:374). Synthetic lethality: produces a phenotypic effect opposite to that of suppression. In this case, the deleterious effect of one mutation is greatly exacerbated (rather than suppressed) by a second mutation in a related gene (a) The observation that double mutants with two defective proteins (a and b) have a wild-type phenotype but that single mutants have a mutant phenotype indicates that the function of each protein depends on interaction with the other. (b) The observation that double mutants have a more severe phenotypic defect than single mutants is also evidence that two proteins (e. g. , subunits of a heterodimer) must interact to function normally. (c)
