Specialized Chromosomes and Their Uses in Caenorhabditis elegans - Caenorhabditis Elegans: Molecular Genetics and Development - page 36

chromosome I is inverted, and in mlnl, a large section of the center of chromosome II
from lin-31 to rol-1 is inverted.

1. Uses of Inversions
Inversions have been used effectively both as balancers ( Fig. 3 ) and for capturing
novel mutations. Lethal mutations, along with more complex rearrangements such
as deletions, have been recovered with both hIn1 and mIn1 ( Bosher et al., 2003;
Edgley and Riddle, 2001; Zetka and Rose, 1992 ). Similar to other balancers, inver-
sions may be more effective when marked with either a lethal or visible mutation. In
the case of hIn1, mutations in unc-75 and unc-54 were induced on the inverted
chromosome ( Zetka and Rose, 1992 ). Eight variant strains of mIn1 have been
isolated, an unmarked form, ones that carry recessive morphological or lethal
markers, and one that carries an integrated transgene that confers a semidominant
GFP phenotype, making mIn1 useful for a wide variety of applications (M. Edgley,
pers. comm.).

2. Advantages and Disadvantages
An advantage in the use of inversions is that the genomic disruption is limited to
one chromosome and as a result inversions tend to be stable. Any recombination
events that occur with the wild-type chromosome are detrimental to the organism,
and are thus eliminated from the population. A disadvantage can be that inversions,

Fig. 3 Schematic showing segregation from an inversion. In this example, the inversion hIn1 is
balancing a mutation (mut-x). From the self-progeny of this strain 1 / 4 will display the homozygous inversion
phenotype (unc-54), / 2 will be the balanced heterozygous animals, and 1 / 4 will be homozygous for the

balanced mutation and will display the mut-x phenotype. The strain can be successfully maintained by
selecting the WT animals in each generation.

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