Believe it or not, quite a bit of math modeling went into the making of this mod. I can't explain every decision I made, but ultimately the goal was to make the occurrence of a trait match that of vanilla.

Polygene Traits:

General population initial distribution: 1/6 receive AA, 4/6 receive Aa, 1/6 receive aa.

This gives a distribution of: (Numbers represent number of alleles, ex: aaBbCc = 2)

0 -- 0.46%
1 -- 5.56%
2 -- 23.61%
3 -- 40.74%
4 -- 23.61%
5 -- 5.56%
6 -- 0.46%

Trait chances:

At 0: 30% imbecile, 50% slow, 20% dim
At 1: 5% imbecile, 20% slow, 50% dim
At 2: 2% slow, 8% dim
At 3: Nothing
At 4: 2% quick, 8% bright
At 5: 5% genius, 20% quick, 50% bright
At 6: 30% genius, 50% quick, 20% bright

Multiplying the distribution with the chances gives:

Imbecile: 0.42% + 0.10% random chance + 0.10% from existing imbeciles = 0.62%
Slow: 1.83% + 0.25% random chance + 0.20% from existing slow = 2.28%
Dim: 5.561% + 1.00% random chance + 0.50% from existing dim = 7.16%
Bright: same as dim
Quick: same as Slow
Genius: Same as imbecile

The attractiveness, height, and strength trait groups are modeled in almost the exact same way.

Mendelian Traits:

Several of these have different trait chances. In terms of how common they are: Stutter = Lisp > Hunchback = Clubfoot = Harelip > Dwarfism

Anyway, for the deformities, the number of alleles are not relevant - the number of RECESSIVE alleles are. The presence of one dominant allele in the pair deactivates the possibility of the genotype.

So the distributiion is: (Numbers represent number of recessive alleles: AaBbcc = 1)

0: 72.90%
1: 24.30%
2: 2.70%
3: 0.10%

Trait chances:
0: N/A
1: 0.5% chance for, say, hunchback
2: 7.5% chance for hunchback
3: 75% chance for hunchback

Multiplying gives:

0.40% + 0.10% random chance + 0.10% existing trait = 0.60%