Screens, selections, and mutants - AndersenLab/Genetic-Analysis GitHub Wiki
Isolating Mutants: Selections vs. Screens
Mutant individuals can be isolated using a genetic selection or a genetic screen. The easiest way to differentiate between the two is to consider the growth condition that is used.
In a selection experiment, the growth environment will be chosen to propagate only a certain class of mutant. For example, a selection experiment might seek to identify mutants that can tolerate a lethal toxin. Cells that grow might have a loss-of-function mutation in a protein involved in the import of the toxin.
Contrast this situation with a genetic screen. In this type of experiments, the growth environment is not altered - and mutants and non-mutants will grow together. Oftentimes, you require an assay or visual inspection to differentiate mutant from wild-type progeny. For example, consider a strain of yeast that typically turns black in response to an environmental additive. However, mutants of a particular gene in a pathway will turn red, rather than black. Both mutants and non-mutants survive in the growth conditions and can be identified based on their color.
Balancer Chromosomes
Balancer Chromosomes are an important tool used to perform genetic crosses and isolate mutants. Every balancer chromosome has three attributes in common:
- contains many inversions to produce lethal chromosomes if recombination occurs
- confers an easily scored dominant phenotype
- is recessive lethal