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provocative_bear t1_ivd2av8 wrote

You better believe it! The textbook case for this is the "sickle cell" trait. This is the gene that causes sickle cell anemia, a horrible genetic disease where your red blood cells are all jacked up and you mostly die a slow painful death. So why is this gene still hanging around humans' genomes if it kills people? If you are merely a carrier of the gene or have "sickle cell trait", it provides substantial protection against death from malaria (and the symptoms are much milder than full-blown sickle cell anemia). It makes your red blood cells far more resistant to being infected by the disease-causing agent, the plasmodia The crossed-out text was somewhat recently debunked, it looks like the plasmodia either struggles to survive in the mutant red blood cells, or the infected red blood cell is more efficiently removed from the body before it bursts with a payload of new plasmodia.

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Prasiatko t1_ive0t16 wrote

Similarly Cystic Fibrosis is thought to have stuck around as being a carrier makes you significantly more likely to survive a cholera infection.

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lloydthelloyd t1_ivecx1d wrote

And recently a gene linked to arthritis has been found to possibly be more prevalent because it fended off bubonic plague...

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Distinct_Comedian872 t1_ivfhcxx wrote

And recently a study showed that if you have Crohns disease, that mutation likely helped your ancestor to survive the plague.

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Barne t1_ivg73ps wrote

another (purported) bubonic plague adaptation -> HIV immunity. CCR5 gene, homozygous delta32 deletion will not allow the HIV virus to infect you. 1% of caucasian population has this

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MulhollandDr4kSB_pls t1_ivehgta wrote

Another example is Thalassemia, a sickness where blood cells have a different structure, protecting the affected from malaria.

Unfortunately, if 2 people with thalassemia (minor) have a child, there will be a 25% chance the kid will have a for of thelassaemia major, which means they need a blood transfusion every few months, otherwise they will die.

This is why in countries where malaria is prevalent, couples are encouraged to do a blood screening before having children to prevent this scenario.

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Dr_JA t1_ivejqyy wrote

In some countries you cannot get married before getting tested as a couple. Testing is mandatory.

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[deleted] t1_ivepumj wrote

[removed]

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Dr_JA t1_iveqwym wrote

Absolutely true. However, I think the countries that implement this specific mandatory screening might have issues that are further down slippery slopes...

I just wanted to highlight that this genetic condition, even though relatively unknown in the US/EU, has consequences even for many people in other countries.

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mitharas t1_iveuzzl wrote

> This is why in countries where malaria is prevalent, couples are encouraged to do a blood screening before having children to prevent this scenario.

So when the test indicate the above scenario, people just... don't have offspring? This seems like a rather volatile social situation.

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cathbad09 t1_ivf09k5 wrote

If I had a chance of bringing a child into the world with some genetical condition I’d want to factor that into my decision making

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Cherry5oda t1_ivf6u2k wrote

According to Wikipedia in Iran they are directed to genetic counseling if they are carriers. In India the testing is voluntary and marriage is discouraged if they are both carriers.

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MulhollandDr4kSB_pls t1_ivfczif wrote

Either that or adoption or artificial fertilization. Or they decide to get children anyway.

But at least they can consult with a doctor and make an informed decision whether to take the risk or not.

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fastspinecho t1_ivfnvu8 wrote

Or they could get prenatal screening after pregnancy.

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[deleted] t1_ivep1ew wrote

>It makes your red blood cells far more resistant to being infected by the disease-causing agent, the plasmodia

It's because one of the life stages of malaria requires for the parasite to mature inside red blood cells (RBCs), before the cell bursts and all the mature parasites are released into the blood stream.

With sickle cell disease, the RBCs are more fragile and burst more easily. That means the RBCs are bursting and releasing the parasites into the blood before a lot of them are fully mature, which hurts the progression of the disease.

In the presence of two copies of the gene (one from each parent), that trait is even more pronounced and RBCs are so fragile that they're constantly bursting for no reason, which causes anemia and all sorts of body-wide problems. Day to date events like stress, high temperature or dehydration can cause them to burst en masse and cause pain attacks.

Also the name is because the RBCs are literally shaped like a sickle instead of being kind of round.

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First_Foundationeer t1_ive7llh wrote

Thalassemias, in general, are hypothesized (and, empirical agreement was found for alpha-type) to function in a similar manner.

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-there_is_hope- t1_ivehynk wrote

To add onto this, this effect is called the heterozygote advantage wherein the heterozygous genotype has greater fitness than the homozygous dominant or recessive genotype.

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