People with down Syndrome

This week, we learned a lot about genetics. But, there’s always two sides to a story. There’s the good side where the study of genetics can help us learn more about our past and our future. Then, there’s the down side where we discover the shocking amount of diseases that are traveling among the human population. One down side in particular, Trisomy 21 or down syndrome, is a commonly heard disorder that results from the presence from either all or part of an extra Chromosome 21.

It is a common birth defect, the most frequent and most recognizable form of delayed mental growth, appearing in about 1 of every 700 newborns a year. Although the syndrome had been described thousands of years before, the suspected association of down syndrome with a chromosomal abnormality was first confirmed in 1959. Many persons with down syndrome are often referred to as institutionalized but reality is, not all persons with down syndrome are with mental delays. Health problems associated with that syndrome sometimes receive little to no medical care, and many patients would die prematurely in infancy or early adulthood. Nevertheless, working against this negative reality, community-based associations have been created to support persons with down syndrome.

One character often associated with down syndrome is Kenny the White Tiger. While much speculation holds Kenny as being alive, others report that Kenny died back in 2008. Some even say that diagnosis of down syndrome is in question in Kenny’s case. Tigers have 19 chromosomes while humans have 23. They say that while Kenny’s face does bear a superficial resemblance to that seen in people with down syndrome, it’s far from clear that this was the result of a third copy of any chromosome, let alone one that could be matched to our 21st.

Since Kenny is technically considered a part of the greed of the breeding industry, it is not unknown that white tigers are rather rare. With so few of them, the genetic pool is limited and inbreeding is sadly an inevitable consequence. The strange thing is, Kenny’s parents were brother and sister. Most of his siblings were miscarried, or died very young, whereas Kenny lived from the age of two.

One great benefit of having duplicate copies of each of our genes is that the damaging recessive mutations are rarely ever expressed. However, in the off chance where parents are closely related, there is a high chance of them both carrying the same rare version of a gene, with a one in four chance their offspring will inherit it from both sides. With enough damaging alleles in common, this becomes something similar to that of a repetitive game of chromosome roulette.

White tigers are usually an extremely rare case, but many other species suffer when the desire for “perfect” pets leads to inbreeding. One such example is “purebreeds” of domestic dogs and horses, which suffer from many genetic problems which can shorten lifespans, or even cause ongoing disability and pain. However, the tragedy is doubled in the case of tigers, if it were not for the obsession with breeding “pure whites”, these creatures could be allowed to mate with other tigers and preserve the endangered species and maybe even continuously reproduce more offspring naturally.

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