Inbred strains of Saccharomyces cerevisiae carrying MAL1, MAL2, or MAL6 in a common background were used to construct (i) homo- or heterozygous diploids carrying one or two active alleles of a single MAL locus (MAL1, MAL2, or MAL6) and (ii) triploids carrying one, two, or three active alleles of MAL2. The diploid and triploid strains were used to investigate gene dosage effects of the different...

Six triploid individuals were found in a full-sib family of 11 adult rainbow trout (Salmo gairdneri) from a domesticated hatchery stock. The triploid individuals were normal in size and external appearance, had underdeveloped gonads, and showed no evidence of 3n/2n chimerism or mosaicism. XXY triploids were males, suggesting that the Y chromosome is male determining in trout. Because they may a...

Silkworm (Lepidoptera) males produce dimorphic sperm: nucleate eupyrene sperm and anucleate apyrene sperm. The eupyrene sperm are ordinary sperm to fertilise the eggs, while the function of apyrene sperm remains uncertain. After meiosis, 256 sperm cells are enclosed by a layer of cyst cells, forming a sperm bundle. We have previously documented that the nucleus of eupyrene sperm anchors to the ...

HE banana breeding program currently being carried out in Jamaica T is largely based on the progeny of the triploid (zn=33) Gros Michel crossed with a number of naturally occurring diploids. The bulk of such progeny have been found to be tetraploid (LARTER 1935 and unpublished; CHEESMAN and DODDS 1942), which suggests that Gros Michel has a tendency to throw a majority of triploids among its vi...

Polyploidy plays a prominent role in the speciation process in plants. Many species are known to be part of agamic complexes comprising sexual diploids and more or less exclusively asexual polyploids. However, polyploid formation has been studied in very few cases, primarily because of the challenges in examining these cases phylogenetically. In this study, we demonstrate the use of a variety o...

The Squalius alburnoides complex (Steindachner) is one of the most intricate hybrid polyploid systems known in vertebrates. In this complex, the constant switch of the genome composition in consecutive generations, very frequently involving a change on the ploidy level, promotes repetitive situations of potential genomic shock. Previously in this complex, it was showed that in response to the i...

new findings of non-disjunction in autosomes of triploid females and of males carrying inversions in their autosomes seem to be desirable. It should be noted that cases of autosomal non-disjunction in males which carry inversions have already been found by Dobzhansky2 (1933) and by J. Schultz (unpublished). Dobzhansky and Darlington have observed cases of non-disjunction of autosomes cytologica...

Early reproductive effort and growth were measured in 3 groups of the Pacific oyster Crassostrea gigas: 1 diploid group and 2 triploid groups resulting from either chemical induction (3nCB) or crosses between tetraploid and diploid parents (3nDT). Oysters were reared under intensive nursery conditions and sampled when 5 mo old. Reproductive effort was estimated by crosssectional area measuremen...

Knowledge of rangewide variation in DNA content and ploidy level may be valuable in understanding the evolutionary history of a species. Recent studies of Acacia senegal report diploids and occasional tetraploids in the Sudano-Sahelian region of sub-Saharan Africa, but nothing is known about the overall extent of DNA ploidy variation within the species. In this study, we determine the DNA conte...

A selective system for recovery of exchanges between trans mutations at adjacent loci, l(3)S12 and rosy, is described. In addition to the expected crossover and conversion classes, two exceptional types of offspring were recovered. Triploid offspring arose as 0.01% of all zygotes; the diploid chromosome set was apparently of maternal origin. Nine tandem duplications derived from unequal exchang...