What is the best explanation for how we can exhibit so many different traits from so few genes

Alleles of a gene are responsible for different traits

Explanation:

There are several variant of a gene which in pair leads to varied phenotypic characteristics or traits.

For instance, there are three alleles for blood group i.e A, B and O but there are in totality there are basic 8 blood groups including the categorization on the basis of Rh factor.  

Likewise, there are several variations of skin color; however there are majorly six genes that are responsible for skin color.  

So, basically alleles of a gene are responsible for different traits

enzymes loose their form in both unsuitable ph and temprature.

Explanation:

at very high tempratures enzyme molecules denatures due to high speed movements, at low tempratures enzymes works too slow to be useful enough.

low ph solotions contain lot of H+  and high ph solutions have few H+ , and the number of these H+ ions have polar effects on enzymes.  some Enzymes like pepsin works perfect in acidic environment ( ph=2)  while others might work at  high ph  or average ph( like Trypsin  works well at ph=7).