Figure 2.

Recessive screens for defects in mouse immunity. One of two breeding strategies that can be used for large-scale screening programs is illustrated. Ethylnitrosourea (ENU) is used to generate a high burden of mutations in the germ line of male mice in the G0 generation (approximately 100 per male). These mutations are transmitted by breeding with wild-type females (Mating A), creating a panel of progeny in the G1 generation that are heterozygous for some of the mutated alleles. Males of this G1 generation can again be bred to wild-type females (Mating B), leading to a large family of individuals in the G2 generation, many of which are heterozygous for mutated alleles. Female G2 mice, when bred with their G1 father (Mating C), bear progeny of whom some will be homozygous for an ENU-induced mutation. Alternatively, G1 males and unrelated G1 females can be crossed, and the G2 progeny of these mice can participate in brother-sister matings that can generate homozygotes. Adapted from [22].