Genome structure and chromosome function

Aneuploidy refers to the loss or gain of individual chromosomes or loss of a portion of an individual chromosome from the normal chromosome set. The resulting gene-dosage imbalance may or may not noticeably affect phenotype. Although its phenotypic manifestations are usually apparent, information about the underlying alterations in structure, expression, and interphase organization of unbalanced chromosome sets is still sparse. Aneuploidy is the most common chromosomal aberration in plants, and aneuploids are valuable for the study of chromosome evolution, phenotypic manifestation of chromosome loss or gain, and mapping genes and genome. Breeding programs intended to transfer desirable genes from one species to another produce addition lines as intermediate crossing products. Such aneuploids can be used for further introgression, but their abnormal recombination and segregation interfere with production of stable introgression lines. They can have specific morphological characteristics, but more often additional confirmation is needed. Their genetic and cytogenetic properties make them powerful tools for fundamental research on regulation of homeologous recombination, distribution of chromosome-specific markers and repetitive DNA sequences, and regulation of heterologous gene expression. Recent advancements and availability of genomic resources have widened the scope for their use. They make possible assignment of individual linkage groups to specific chromosomes and can improve identification of quantitative trait loci (QTLs) and underlying DNA components/sequences.