Hyla versicolor, a tetraploid treefrog, is reported to have originated via multiple hybridization events involving three diploid ancestors. Its complex reticulate history provides insights into the roles that polyploidy and hybridization can play in the origin of species.

Some genomes are known to have incurred a genome doubling (tetraploidization) event in their evolutionary history, and this is reflected today in patterns of duplicated segments scattered throughout their chromosomes. These duplications may be used as data to "halve" the genome, i.e. to reconstruct the an cestral genome at the moment of tetraploidization, but the solution is often highly non-un...

In yeast, the enzymes required for steps (1) to ( 3 ) are “induced” enzymes which are synthesized only if galactose is present in the medium (DE ROBICHONSZULMAJSTER 1958). The nonallelic genes GA, and GA, are required in our strains of Saccharomyces for the rapid fermentation of galactose. GA, appears to control the transfer of galactose into the cell (DOUGLAS and CONDIE 1954) ; in the absence ...

A new human myeloid cell line has been established recently from the bone marrow cells of a patient with chronic myelogenous leukemia in blast crisis. The active proliferation and survival of the cells in RPMI 1640 medium containing fetal calf serum are clearly dependent on the presence of either natural or recombinant human granulocyte-macrophage colony-stimulating factor (rhGM-CSF). Despite p...

Tetraploidy can constitute a metastable intermediate between normal diploidy and oncogenic aneuploidy. Here, we show that the absence of p53 is not only permissive for the survival but also for multipolar asymmetric divisions of tetraploid cells, which lead to the generation of aneuploid cells with a near-to-diploid chromosome content. Multipolar mitoses (which reduce the tetraploid genome to a...

Genomic instability is characteristic of cancer cells, and promotes the accumulation of genetic lesions that contribute to their neoplastic progression. There are at least two general mechanisms by which cells exhibiting genomic instability can depart from the diploid state. One involves DNA damage from high levels of translocations, gene amplification or other chromosomal anomalies. The other ...

An increase in chromosome number, or polyploidization, is associated with a variety of biological changes including breeding of cereal crops and flowers, terminal differentiation of specialized cells such as megakaryocytes, cellular stress and oncogenic transformation. Yet it remains unclear how cells tolerate the major changes in gene expression, chromatin organization and chromosome segregati...

Polyploidy, or whole genome duplication, has been an important feature of eukaryotic evolution. This is especially true in flowering plants, where all extant angiosperms have descended from polyploid species. Here we present a broad comparative analysis of the effect of polyploidy on flowering plant diversity. We examine the widely held hypothesis that polyploid flowering plants generate more d...

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