Quote Originally Posted by blackcrystal22 View Post
The spider gene is something called recessive lethality. Now I know you're going to say "but it's dominant" but let me explain. Capitol X will represent the spider gene, and x will represent a normal gene.

Recessive lethality means that the trait (in this case, the spider gene) shows in a heterozygous animal (making the gene 'act' dominant in nature).
[Xx] - Living spider.

However, when the animal is homozygous for the spider gene [XX], the animal dies before it is born. Thus, the lethality is recessive because the gene needs both alleles in order for the lethality to take place (death of the animal). This makes the gene recessive for death, but dominant acting with a heterozygous individual [Xx] but it can still produce normals [xx]. Normals seem less common because of the lethality and the ratio favors the spider gene.

1:2:1 (XX:Xx:xx) And since [XX] dies, you only see the 2:1 ratio of spiders:normals.

Hope that can clear things up a little bit. This is something that I brought up under deep discussion in my genetics class.
I'm far too dumb to understand all that...

If I breed two spiders together, will half the babies (or eggs) be slugs, or will they not even be laid...i.e...be reabsorbed before being laid?