In the strains,
we sometime see

outcrossed: x
Outcrossed: x0
Outcrossed: x2

Whats their difference in between?


This refers to how many times the strain has been outcrossed back to WT.

In addition to the mutant isolated, a mutagenesis causes a lot of collateral damage to other genes. Outcrossing means how many times a given mutant has been backcrossed to the parental strain to eliminate unwanted mutations. Outcrossing attempts to reduce the likelihood that the phenotype you observe is due to one ore more of these other mutations. Two mutant alleles of a gene helps, but does not remove, these concerns.

x: probably means no info given–assume no outcrossing
0x: mean no outcrossing
2x: means the strain carrying the mutation has been obtained after two separate matings to wild type. Typically N2 males are mated into your mutant hermaphrodite, the (het) males (1x) from this cross are taken and mated back to N2 hermaphrodites. Cross-progeny hets are taken and homozygosed. These would be 2x outcrossed. If you have a genotyping strategy, you can keep crossing the 2x hermaphrodites (het or homozygous) to N2 males, following your mutation during each step.

We typically outcross 6x to our lab’s N2 strain. It’s important to note that not all N2’s are the same (see WBG article on that), and that it’s unclear whether outcrossing does what it’s supposed to do: dilute the bad genes 50% at each step.


thankss a lot … ;D