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Once a set of mutations affecting one pathway or
process has been identiﬁed in the haploid products, mutants
are crossed to produce a diploid cell for complementation
testing. The diploid containing two different mutations is
then sporulated and during meiosis the chromosomes are
reshufﬂed by independent assortment and recombination.
Some of the haploid spores will contain both mutations. If
the mutations are in different genes, the cells will have the
wild-type phenotype. (See Chapter 5 of the main textbook
for more on genetic analysis in yeast using tetrad analysis.)
The ability to easily isolate many mutants and the development of clever mutant screens makes possible the sophisticated analysis of gene function and the interaction of
several genes in a pathway. Dominant gain-of-function mutations are particularly useful for pathway analysis using
epistasis tests. Consider a pathway that involves a series of
proteins in a protein kinase cascade in which each protein
phosphorylates and activates the next protein in the pathway (A -> B...
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- Spring '08