A new type of radiation-sensitive mutant of S. cerevisiae is described. The recessive radH mutation sensitizes to the lethal effect of UV radiations haploids in the G1 but not in the G2 mitotic phase. Homozygous diploids are as sensitive as G1 haploids. The UV-induced mutagenesis is depressed, while the induction of gene conversion is increased. The mutation is believed to channel the repair of...

A study was undertaken to determine the relationship between chromosome composition and embryo development. Bovine cumulus-oocyte complexes were matured in vitro and exposed to semen from one of three different bulls, one of which was a 1/29 Robertsonian translocation carrier. There were no significant differences among the three bulls in their sperm penetration or in the cleavage or developmen...

It has long been known that diploid strains of yeast are more resistant to 7-rays than haploid cells, and that this is in part due to heterozygosity at the mating type (MAT) locus. It is shown here that the genetic control exerted by the MAT genes on DNA repair involves the a1 and a2 genes, in a R M E l independent way. In rad18 diploids, affected in the error-prone repair, the a/a effects are ...

Cassava breeding is difficult and, compared with other crops, inefficient. The problems in cassava breeding relate to the length of the breeding cycle, the large genetic load present in the crop, and the heterozygous nature of the parents and progenies evaluated. The production of doubled haploids, through tissue culture techniques, offers interesting advantages. By definition, any process that...

Doubled haploid (DH) technology has been used in breeding programs for several decades and is currently the method of choice in a number of crop species, including barley (Hordeum vulgare L.), rapeseed (Brassica napus L.), maize (Zea mays L.), and wheat (Triticum aestivum L.). In this study we investigated via computer simulation the benefit of using DHs compared with the conventional wheat bre...

ENE action has often been studied by investigating gene dosage relaG tions. This has been done by the addition of chromosome fragments or of entire chromosomes to different genetic backgrounds, exemplified by the work of SCHULTZ (1935) for the gene shaven in Drosophila and of BLAKESLEE (1930) in Datura. STERN and HEIDENTHAL (1944) have shown by their work on position alleles in Drosophila that ...

Anthers of Nicotiana tabacum cultivar Wisconsin 38 were treated with the mutagen ethyl methane sulfonate and cultured to obtain populations of haploid plants of high genetic variability. The selection of these populations by their photosynthetic efficiency was carried out in a hydroponic culture chamber with a CO(2) atmosphere concentration close to the compensation point. Plants that survived ...