Polyspermy is a major puzzle in reproductive biology. In some taxa, multiple sperm enter the ovum as part of the normal fertilization process, whereas in others, penetration of the ovum by more than one sperm is lethal. In birds, several sperm typically enter the germinal disc, yet only one fuses with the female pronucleus. It is unclear whether supernumerary sperm play an essential role in the...

Spermatid injection into the oocyte cytoplasm has been shown recently to yield viable human embryos developing to term after transfer to the mother. This study provides details of the laboratory techniques related to round spermatid injection (ROSI) and elongated spermatid injection (ELSI) and focuses on some special features of zygote development associated with the use of these types of sperm...

Cells encounter up to 10 6 DNA damages per day, which can be induced by exogenous physical agents, spontaneous chemical reactions , and products of endogenous metabolism. 1 To cope with these threats, the DNA damage response (DDR) system is employed to detect and repair these damages. if massive DNA damages occur within cells which cannot be repaired properly or promptly, the DDR will cause apo...

The technique of introducing new genetic material into the germline of mammals has been a major development in biotechnology over the last decades. ”Transgenic animals“ are animals whose chromosomes contain stable, integrated copies of exogenous genes, additional copies of endogenous genes or gene constructs. They are frequently created by two different techniques: microinjection of DNA into th...

Vinblastine is shown to induce pronuclear fusion failure in conjugating Tetrahymena thermophila. In this alternate conjugational pathway gametic pronuclei are exchanged between conjugants but do not fuse. Each pronucleus undergoes one mitotic division to produce a new macro- and micronucleus. Genetic consequences of pronuclear fusion failure include the following: (1) the progeny are whole geno...

Cortical granules are secretory vesicles poised at the cortex of an egg that, upon stimulation by sperm contact at fertilization, secrete their contents. These contents modify the extracellular environment and block additional sperm from reaching the egg. The role of cortical granules in blocking polyspermy is conserved throughout much of phylogeny. In the sea urchin, cortical granules accumula...