1.14.9 Whole Genome Duplication Definition

Whole Genome Duplication Definition is a description of a specific type of genomic event in which the entire chromosome complement of a cell is doubled within a single cell cycle, converting a cell of a given ploidy into a cell with twice that number of complete chromosome sets, most commonly transforming a diploid cell into a tetraploid cell. Whole genome duplication refers to a discrete, identifiable event of complete genome doubling, distinguished from the gradual, piecemeal accumulation of individual chromosome gains characteristic of other forms of numerical chromosomal change.

Conceptual Basis

Doubling of the Entire Complement in One Step

Whole genome duplication is defined by the simultaneous doubling of every chromosome in the genome as a single coordinated event, rather than through the sequential gain of individual chromosomes over multiple divisions. Following whole genome duplication, the cell possesses two complete copies of what was previously its full chromosome set, each chromosome and its associated genes present in double the prior dosage.

Relationship to Polyploidy

Whole genome duplication is the process by which a diploid cell most commonly becomes polyploid, typically tetraploid, and represents one of the principal routes by which a polyploid cellular state arises, though polyploidy can also result from other processes such as cell fusion or endoreplication.

Mechanistic Basis

Cytokinesis Failure

A common route to whole genome duplication is the failure of cytokinesis following an otherwise completed round of DNA replication and chromosome segregation. When the cytoplasm fails to divide after chromosomes have separated, the resulting single cell retains the full chromosome complement of both would-be daughter cells, achieving a doubled genome within one nucleus or a shared cytoplasmic compartment.

Mitotic Slippage

Whole genome duplication can also arise through mitotic slippage, a process in which a cell that has been arrested in mitosis, often due to unresolved spindle assembly checkpoint signaling, exits mitosis without completing division, reverting to an interphase-like state while retaining the doubled chromosome content that had already been replicated.

Cell Fusion Contributing to Genome Doubling

Fusion between two cells can also produce a genome-doubled state functionally similar to whole genome duplication, by combining two complete chromosome complements into a single cell, although this route involves the merger of two separate cells rather than doubling within a single cell.

Immediate Consequences

Formation of a Tetraploid Intermediate

The most immediate and direct consequence of whole genome duplication in a previously diploid cell is the formation of a tetraploid cell, containing four complete chromosome sets in place of the usual two, with dosage balance preserved across all chromosomes since the entire complement was doubled proportionally.

Supernumerary Centrosomes

Because centrosome duplication is normally coordinated with the cell cycle, a whole genome duplication event frequently leaves the resulting cell with more centrosomes than the number appropriate for its new, doubled chromosome content, predisposing subsequent divisions to abnormal, multipolar spindle formation.

Downstream Significance

A Route to Subsequent Aneuploidy

A whole genome duplication event does not itself alter the proportional balance among chromosomes, but the resulting excess of centrosomes and chromosomes increases the probability of missegregation during the divisions that follow, so that whole genome duplication frequently precedes and predisposes toward the emergence of aneuploidy and chromosomal instability in the descendant cell lineage.

Distinction From Gradual Aneuploid Accumulation

Because whole genome duplication doubles the entire chromosome set in a single, proportionally balanced step, it is mechanistically and conceptually distinct from the gradual, chromosome-by-chromosome accumulation of numerical imbalance that characterizes ongoing chromosomal instability, even though the two processes are frequently linked in sequence within a cell lineage.