A number of humans have something called the photic sneeze reflex – there’s a reasonable chance you have it since it affects a quarter of the population. If you’ve ever sneezed when you step into bright sunlight, then you have it.
Scientists are, to put it mildly, baffled about why this happens. However, it’s clear it’s genetic – if one of your parents has it, you have a fifty percent chance of also having it. While sneezing isn’t really dangerous, having a weakness for bright lights during driving or operations can pose some interesting problems.
These Feet are Deadly Weapons
Genetic and environmental factors combine to create something called clubfoot, where one of the feet or both are rotated inward and downward on newborn children. The foot and leg may also be smaller than is normal, but various treatments are available to correct the issues. These include casting, manipulation of the Achilles tendon, braces, and surgery.
Without this help walking can be painful and difficult, though as long as it's treated with time, people who have developed clubfoot usually have no issues in life other than an interesting fact about themselves. It's more common, for some reason, in first children as well as males.
No Colors Here
Color blindness – or color vision deficiency – is the decreased ability to see color or differences in color. There are several versions, including total color blindness where the sufferer only sees in shades of gray. The most common cause of this disorder is a genetic problem in the development of the eyes' cone cells, which sense color.
Since the genes that carry these problems are on the X chromosome, men suffer from this disorder far more than women. The disorder makes people unable to have certain jobs, including pilots, train drivers, and many positions in the armed forces.
Dry Earwax? Wet? Sticky? Your Genes Decide
Earwax is pretty much a human constant, but there are a bunch of different versions. Some of it is dry, flaky, and gray, while other people produce it wet, yellow, and sticky. It's all because of one gene, ABCC11.
The version of the gene – called an allele – determines the production of this substance. That's about it as far as the reasoning goes, but the same gene is also responsible for body odor, primarily the smell of your armpits. If you have wet, sticky earwax, there's a bigger chance to have a stronger body odor.
Going to Bed Late or Getting up Early
We all have a part of the day when we feel most alert, awake, and productive. You might be a night owl or a morning lark, or you might be some time in between, but once again this is all thanks to our genes.
Our circadian rhythm runs on a twenty-four-hour schedule, but genes can slow it down or speed it up slightly. Those who have a fast rhythm will feel full of energy in the morning but crash at night, while those with a slow rhythm will be slow in the morning and have lots of energy at night.