BIOL207 B01 Lec09
CHAPTER 4 (cont’d)
A. Complementation testing
1. Given two mutants with the same phenotype, how do we know whether
these mutants have defects in the same gene, or in different genes?
2. Many mutants affect biochemical pathways, or other types of pathways;
example of network of biochemical pathways here:
defects in different genes in the same pathway can have similar effects, i.e.
no wild-type end product is produced
i. e.g. purple pigment synthesis (anthocyanin) has dozens of enzymes
that act on colourless precursors (= intermediates); mutation can
give white flowers
3. Complementation test shows whether independent mutants affect the same
gene or different genes
i. Need to have fully dominant alleles, e.g. wild-type allele is
ii. Cross i