Some behavior can be traced to the genome. In Drosophila there are many interesting studies that show how genes and courtship behavior are related Example.
In mammals, the environmental component in determining courtship behavior is for sure, much more relevant than in Drosophila.
Regeneration of complex tissues like limbs is known in many animals. Salamander has been used as a model for limb regeneration. During regeneration, the cells at the amputation site de-differentiate to form what is known as a blastema which in turn differentiates to form different kinds of cells.
Christen et al. (2010) have found that de-differentiation in ...
What is a pluripotent stem cell?
A pluripotent stem cell is a cell that can differentiate into any of the major tissue categories. Every animal exists as a collection of pluripotent stem cells at an early stage of development: if you are looking for an evolutionary purpose, that's where you should start, and the purpose is pretty obvious: you start as a ...
A secondary oocyte contains n/2C genome and a sperm fuses with a cell with n/C genome (matured ovum). Therefore a secondary oocyte must divide and eject a polar body and that happens due to fertilisation.
so the answer is after fertilisation and before entry of sperm.
Male gametes (aka sperm) is produced by meiosis of numerous germ cells (gametes precursors). It is unlikely that all germ cells have damaged DNA so the newly produced gametes should be healthy. This also implies that if the DNA inside the gametes was damaged after they were produced, then again, the new gametes will be healthy.
As a disclaimer, I am talking ...