Cytogenetics and the evolution of medical genetics

What That Purple Comb Says About Your Chickens

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A Mutation Story:

A gene known as HbS was the center of a medical and evolutionary detective story that began in the middle 1940s in Africa. Doctors noticed that patients who had sickle cell anemia, a serious hereditary blood disease, were more likely to survive malaria, a disease which kills some 1.2 million people every year. What was puzzling was why sickle cell anemia was so prevalent in some African populations.

How could a "bad" gene -- the mutation that causes the sometimes lethal sickle cell disease -- also be beneficial? On the other hand, if it didn't provide some survival advantage, why had the sickle gene persisted in such a high frequency in the populations that had it?

The sickle cell mutation is a like a typographical error in the DNA code of the gene that tells the body how to make a form of hemoglobin (Hb), the oxygen-carrying molecule in our blood. Every person has two copies of the hemoglobin gene. Usually, both genes make a normal hemoglobin protein. When someone inherits two mutant copies of the hemoglobin gene, the abnormal form of the hemoglobin protein causes the red blood cells to lose oxygen and warp into a sickle shape during periods of high activity. These sickled cells become stuck in small blood vessels, causing a "crisis" of pain, fever, swelling, and tissue damage that can lead to death. This is sickle cell anemia.

But it takes two copies of the mutant gene, one from each parent, to give someone the full-blown disease. Many people have just one copy, the other being normal. Those who carry the sickle cell trait do not suffer nearly as severely from the disease.

Researchers found that the sickle cell gene is especially prevalent in areas of Africa hard-hit by malaria. In some regions, as much as 40 percent of the population carries at least one HbS gene.

It turns out that, in these areas, HbS carriers have been naturally selected, because the trait confers some resistance to malaria. Their red blood cells, containing some abnormal hemoglobin, tend to sickle when they are infected by the malaria parasite. Those infected cells flow through the spleen, which culls them out because of their sickle shape -- and the parasite is eliminated along with them.

Scientists believe the sickle cell gene appeared and disappeared in the population several times, but became permanently established after a particularly vicious form of malaria jumped from animals to humans in Asia, the Middle East, and Africa.

In areas where the sickle cell gene is common, the immunity conferred has become a selective advantage. Unfortunately, it is also a disadvantage because the chances of being born with sickle cell anemia are relatively high.

For parents who each carry the sickle cell trait, the chance that their child will also have the trait -- and be immune to malaria -- is 50 percent. There is a 25 percent chance that the child will have neither sickle cell anemia nor the trait which enables immunity to malaria. Finally, the chances that their child will have two copies of the gene, and therefore sickle cell anemia, is also 25 percent. This situation is a stark example of genetic compromise, or an evolutionary "trade-off."

Is Blue Waffle Disease A Real STI?

Blue waffle disease is an internet hoax and not a real sexually transmitted infection (STI) that turns the labia or vagina blue. Since its creation in 2010, the notorious "blue waffle disease" photo of a scabbed, infected, blue-tinted labia has circulated on the internet. The picture may look convincing, and unsuspecting people may believe it is real and worry they could get the disease.

Blue waffle—"waffle" referring to a slang term for vagina—is a fake STI. The internet hoax claimed the fake STI turns the labia blue and causes symptoms of real STIs like chlamydia, gonorrhea, and trichomoniasis. Some have claimed this fake STI could only affect vaginas and also cause bruising and lesions. The photos may look terrifying and convincing, but the condition is not real. Not only is blue waffle disease absent from reputable medical texts, periodicals, and websites, but medical experts have debunked it. In 2017, Anita Ravi, MD, a family medicine physician based in New Jersey, confirmed the disease was not real. Christine Greves, MD, an OB-GYN at the Center for Obstetrics and Gynecology at Orlando Health in Florida, also confirmed for Health that she has never heard of the disease and that it's not real. Some have claimed the fictional blue waffle disease has similar symptoms to actual STIs and vaginal infections. No STI or vaginal infection can cause a blue-colored labia like in the fake photo. Genital herpes can cause blistering sores and ulcers that become scabs. A vaginal yeast infection can cause redness and swelling outside the vagina. Chlamydia, gonorrhea, and trichomoniasis also have similar symptoms as vaginal infections, such as abnormal discharge and discomfort. See a healthcare provider if you have discomfort, itching, or any other symptom on or around your vulva or vagina. You will not be diagnosed with blue waffle disease. Tests might show signs of an STI or another condition. You can prevent STIs in many ways. It's important to avoid unprotected vaginal, anal, or oral sex and get vaccinated for hepatitis B and human papillomavirus (HPV). Using condoms can prevent the spread of STIs. You can also decrease the number of sexual partners you have to reduce the chances of getting an infection. STI Testing See a healthcare provider about STI testing if something in your genital area does not feel right or you notice abnormal discharge. Symptoms do not always present right away, so it's important to see a healthcare provider, regardless of whether you were recently exposed. Most routine STI testing involves taking blood or urine samples, but they may not always be accurate. A healthcare provider may also do a swab test to confirm a diagnosis. They will swab the vagina or cervix during a pelvic exam to test the cells or grow bacteria in a lab setting to detect an infection. Results can take anywhere from a few hours to two weeks. Swab results typically take longer than blood or urine testing. Blue waffle disease is an internet hoax that people have identified as an STI, but the disease is not real. Some of the fictional disease's symptoms mimic signs of other STIs, such as sores, swelling, and discomfort. No STI will turn your vagina or labia blue. There's always a risk of getting an STI if you are sexually active, but testing can help you receive a proper diagnosis and treatment options.

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