Identification and distinction among segmental duplication-deficiencies by fluorescence in situ hybridization (FISH)-adorned multivalent analysis

Abstract

Most simple reciprocal translocation homozygotes and heterozygotes are euploid, and normal in genotype. However, translocation heterozygotes form six types of numerically balanced meiotic products. The cross of a translocation heterozygote with a normal individual can yield normal progeny, translocation heterozygotes, or any of four segmentally aneuploid duplication-deficient types (dp-dfs). Using metaphase I configuration analysis, most dp-dfs can be distinguished easily from normal and heterozygous translocations. However, identification of the four dp-df types is often impossible unless there is an appreciable karyotypic difference in arm size, relative breakpoint position, or a diagnostic cytological marker. Here we demonstrated the utility and facility of dp-df identification by means of meiotic fluorescence in situ hybridization (FISH) to adorn one chromosome arm with a molecular marker. The rationale is presented diagrammatically, and exemplified by identifying both adjacent-1 and adjacent-2 dp-dfs in Gossypium hirsutum. Polymorphism is not required among marker loci, so analysis of dp-dfs can proceed without requirement of sexual hybridization or sophisticated high-polymorphism marker systems. Besides facilitating the identification of dp-dfs, such an analysis can provide facile means to assign marker loci to chromosomes, arms, and segments. Integrative mapping of chromosomal, physical, and recombination maps will thus be facilitated. An ability to readily distinguish adjacent-1 and adjacent-2 types of dp-dfs should also enhance strategic derivation of other aneuploids, e.g., dp-df related monosomes and trisomes.Key words: Gossypium, cotton, duplication-deficiency, fluorescence in situ hybridization, repetitive DNA.