How Genes Work and Why they Come in Different Flavors

Even if you haven’t asked yourself why it is that genes makes us sick, perhaps you have wondered why it is that your sister has legs up to her ears and piercing blue eyes that haven’t been seen in the family since Great-Aunt Bessie, while you seem to have inherited a horrible mix of dad’s stockiness and mom’s frumpiness? And what’s up with your brother’s moroseness: Where did that come from?

It is not much of an explanation, but the straight answer is that genetics is a lot more complex than the idea that there’s a gene for every trait. Most traits, or attributes, are regulated by many genes, not just one. Furthermore, while it is a nice abstraction to suppose that genes come in normal, or good, versions and mutant, or bad, ones, the reality is that there are always multiple different flavors of normal. The gradation from the most common allele to various types of normal alleles to abnormality is continuous. Just having certain alleles is insufficient to predict whether a person will get a disease.