Sexual Reproduction

The main problem with implementing sexual reproduction is that since science doesn't even know why actual organisms have sex (there are some theories), so we aren't sure what we really need to implement, if we can take any shortcuts, etc.

There are several, possibly inter-related features of organisms that have sex.

• Dipoidity - Although diploidness is the most common, many funguses even have up to dozens of each chromosome.
• Dominant, Co Dominant and Recessive expression - Most real life genes are either dominant, recessive, or more commonly co dominant. Is this required for sexual reproduction to be effective?
• Crossing Over - A shuffling of the parents' DNA before gifting to the child. Does crossing over need to happen between the parents' DNA itself, or can crossing over work between haploid strains of both parents?
• Chromosomes - Physically seperated sections of DNA. Perhaps to seperate certain genes from being able to cross over with each other? Perhaps totally pointless? If so why do organisms maintain it?

Because relatively little is known for sure about the role each has in sex and evolution, the safest (if most intensive) course of action is to model all of them. "How" becomes a hotly debatable question.