Specialized Chromosomes and Their Uses in Caenorhabditis elegans - Caenorhabditis Elegans: Molecular Genetics and Development - page 38

Fig. 4 Deficiency mapping. In this example, the two mutations, x and y, fall within a genomic region
that is covered by the deficiencies a-g. Complementation mapping will reveal that mut-x falls within the
region defined by the overlap of deficiencies b and c. In the case of mut-y complementation tests will show
that the mutation falls within the region not covered by a deficiency. If two or more such regions are
present mut-y will be ambiguously assigned to all of them.
On an autosome, chromosome V deletions were described as that which could pair
normally and recombine on the pairing (HRR) side of the chromosome and severely
reduce crossing over in the other half of the chromosome. Molecular characteriza-
tion of the rearranged chromosomes using oligoarray Comparative Genomic
Hybridization (aCGH) (see Section III B.) revealed that the extent of the disruption
between homologs correlated with the degree of crossover suppression ( Jones et al.,
2009 ). The results demonstrated that homolog lengths may contribute to the fidelity
of meiotic crossing over and is consistent with the proposed existence of multiple
initiation sites occurring along the chromosome that mediate crossing over, possibly
by facilitating tight alignment of homologs.
3. Allelic Characterization
Deletions have value in the characterization of mutant alleles ( Muller, 1918 ).
Mutations that are phenotypically null are critical for interpretation of gene function,
and valuable for determining the relative severity of other alleles that may alter the
phenotype without eliminating it. Examination of the phenotype of a heterozygote