Our focus on extrinsic differences misses the truth that we are more intrinsically different, more than we can envision. We are a kaleidoscopic pool of phenotypes, genetic traits and disorders.
With a mutation in a gene for collagen – a protein that forms and strengthens bones – some have brittle bones that crack spontaneously. With a mutation in a gene responsible for structural integrity of the skeleton and blood vessels, some grow unusually tall and tend to die of sudden ruptures of the heart.
Some men drink and smoke and die at 70 while some healthy men die at twenty with a sudden heart attack. Some have more fingers than others, and some even bear a permanent odour of fish.
Our intrinsic differences that manifest (sometimes) extrinsically are explained by McKusick’s taxonomy of genetic diseases:
First, mutations in a single gene can cause diverse manifestations of disease in diverse organs.
For example, in Marfan syndrome, a mutation in a structural protein affects all connective tissues. They have recognisably abnormal joints and spines and unobservable, weakness of vessels and arteries. Marfan patients often die young due to rupture of blood vessels.
Second, multiple genes could influence a single aspect of physiology.
For example, blood pressure is regulated through various genetic circuits and abnormalities in one or many of these circuits all result in the same disease – hypertension.
Third, certain genes only become actualised into phenotypes depending upon environmental triggers or random chance.
For example, inheritance of the mutant BRCA1 gene increases the risk of breast cancer dramatically, but not all women with this mutation will develop breast cancer.
Fourth, genetic mutation is merely a variation in a natural environment.
For example, a tall man in a nation of dwarves is a mutant or a blond child in a country of brunettes. The issue then, is not the mutation itself but the disability caused by the mismatch of genetic endowment and the environment.
All in all, our genetic makeup vary vastly, and mutations may by chance, manifest. Why we do we see only physical differences and miss the differences that truly impact our lives?
If we realise that someone who is like us, on the surface, may just drop dead the next minute due to a congenital defect, then what did we have to compare just then? If we realise that someone can suffer emotionally, psychologically just because he was predisposed to, genetically, then why do we judge?
For more information, do read The Gene.