The elven genus was able to interbreed to some extent among its own subraces, as well as with other races.

Elves, like most humanoids, had mostly haploid genes. This is the biological fundament that made interbreeding possible in the first place.

Inter-Subrace

Most separate species were defined by a single allele variation. This group, the standard array, was generally able to interbreed, with the expressed subrace being defined by the dominant allele. The group included high, wood, sun, and - though with a slightly more complicated variation - moon elves. All of these were similar in body structure and other physical traits, differing mostly in skin, hair and eye color, as well as slight ability differences.

The subrace gene, called theifenal, was haploid by nature. Each allele had a Strength factor, which determined which phenotype would be expressed when the gene featured codominant alleles. Some subraces had both dominant and recessive alleles.

Prakash drow/wood elf codominance typically resulted in white-skinned Thanor Prakash drow.

Examples. If you had a Hw (high phenotype) and wW (wood phenotype) interbreeding, you would expect 75% of children to show wood elven traits. If the wood elf parent were instead ww, you would expect 50% wood and 50% high elf children.

If you had a ss (sun phenotype) and Ww (wood phenotype) breeding, you would expect 100% of children to be of wood elven phenotype.

Khali Drow

Khali Drow had a vastly different genetic makeup, featuring notably a triploid sexual gene. Breeding with other elven species was only possible by implanting certain genes into a previously fertilized egg cell.

Inter-Race Breeding

Standard array elves could only breed with certain humanoid races featuring haploid sex genes, though usually only with special means.

Humans

It was fundamentally impossible for any elven species to breed with humans without the help of faeborn potion. Applying faeborn potion to egg cells allowed the uterus to splice donated DNA, selecting specific combinable bits for merging with the egg cell, and the ensuing development of an embryo. Half-bloods usually leaned heavily in looks towards one or the other race, and behaved as a member of that race in further reproduction; however, the presence of the other blood gave half-bloods certain physical traits reminiscent of their other parent, and sometimes showed effects generations later.

Half-elves could be one of two kinds: either de facto elves with some traces of human blood, or de facto humans. The term "half-elf" is sociological rather than biological, as the biological distinction between the two types is much greater than that of each type to its originator species.

Faeborn Potion

Faeborn potion was created by mixing elven and human blood, and adding further substances, to cultivate the production of a specific enzyme called theifenase. Some magical manipulation of factors was also necessary. Potions, when stored in a cool area, could survive for longer periods of time, and greater batches could be created out of an original substrate by a non-caster alchemist by simply mixing in sugarwater or another nutritious substance. There were three kinds of faeborn potions, each designed for application in a certain uterus: standard array elven except moons, moon elven, and human. When inserted into a uterus shortly before fertilization, theifenase was able to mimic sexual reproduction of and inheritance of both parental traits, though always favoring the mother's race in the "half-elf".