that the pollen grains had germinated and that the pollen tubes had penetrated the stylar tissue. Demerec's third suggestion remains as a possibility and a fourth may be added which is likewise untested. The failure of gal pollen to fertilize Gals plants may be independent of stylar interaction altogether, and may involve some abnormal reaction within the ovule, such as inability of the pollen ...

Pde1c is a calcium/calmodulin-regulated, dual-specificity cyclic nucleotide phosphodiesterase. We have used a transposon insertion line to investigate the physiological function of Pde1c in Drosophila melanogaster and to show that the insertion leads to male sterility and male mating behavior defects that include reduced copulation rates. Sterility appears to be primarily due to elimination of ...

Secondary sterility in male patients is due to sperm alterations in a high proportion of cases. But, obstructive azoospermia set up a very important cause of sterility, because a surgical repair is possible. Some of the factors cause obstructive azoospermia are the herniorrhaphy intervention, including secondary inflammatory reaction, and epididymal lesion or epididymitis. Currently, both cases...

Abstract The foundation of potato ( Solanum tuberosum) breeding and the development new varieties is crossing parents to produce seeds that contain combinations alleles may be superior those in either parent. In this review, we begin by highlighting a signature problem breeding, widespread lack fertility observed many lines. We summarize normal male female reproductive structures, fertilization...

Within 10 years of the beginning of experimental genetic research on Drosophila melanogaster, in 1919, A. H. Sturtevant discovered its sibling species, D. simulans. He hybridized the two species and made fundamental discoveries about the genetic basis of hybrid incompatibility. The complete sterility of surviving F(1) hybrids frustrated Sturtevant and his vision of comprehensively exploring the...

What is sympatric speciation? The likelihood of sympatric speciation is perhaps the most controversial aspect of speciation, and certainly one of the most contested questions in evolutionary biology. Speciation in general is defined as the evolution of strong, genetically based ‘isolating barriers’ between populations that prevent them from exchanging genes, for example, mate discrimination, ha...

Apomixis in cassava is formed by aposporic embryo sacs which arise from cells in nucellus or from cells in the sexual embryo sac. There is an association between sterility and apomixis. It seems that sterility caused by defected meioses triggers a specific gene for exhibiting apomixis. This apomictic mechanism is favoured by natural selection since it offers an escape from lethality and provide...

LEVEL: INTERMEDIATE U nder ideal conditions, the result of a sterility test reflects the presence or absence of viable organisms in the samples analyzed. However, it has long been recognized that inferences regarding sterility (whether for a batch of inprocess material or a finished dosage form) are subject to statistical limitations. The probability (P) of detecting contamination in a given ba...

Male sterility of higher plants is a valuable trait used to improve agricultural crops through hybridization. Pollen abortion is a complex and complicated process and the mechanisms involved are actively being studied. Recently, new data on the structure and function of the tapetal cell, changes in Ca distribution, ATPase activity distribution and programmed cell death in anther cells were obta...

We attempted to introgress Y chromosomes between three sibling species of Drosophila: D. simulans, D. sechellia and D. mauritiana. Four D. sechellia Y chromosomes were introgressed into D. simulans without loss of fertility whereas the four reciprocal introgressions (D. simulans Y introgressed into D sechellia) all result in sterility. Both reciprocal Y introgressions of D. simulans and D. maur...