Generation Definitions

N

Number of backcross generations.
Examples: N1, first backcross generation; N2, second backcross generation.

F

Filial or inbreeding (sister X brother) generations.
Examples: F1, first filial generation; F2, second filial generation.

p

Designates the generation when a strain was cryopreserved.
Example: F10p indicates a strain that was inbred for 10 generations and then cryopreserved.

+

Indicates the generation of a strain upon arrival at The Jackson Laboratory. Generation numbers before the "+" took place in the lab of the donating investigator; after the "+", at The Jackson Laboratory.

?

Used when the prior breeding history of a strain is not known.
Example: F?+F12, after arrival at The Jackson Laboratory, we interbred for 12 generations, prior to that remains unknown.

NE

N-Equivalent is used when a mouse from a subsequent backcross generation is crossed back to a mouse from a prior backcross generation.

G

Generation is used primarily in mutagenesis schemes.
Examples: G0 is the mutagenized generation; G1 is the first generation after mutagenesis.