Sickle Cell Anemia Isn’t Half Bad!
Mosquitoes such as this one carry the parasite which causes Malaria
Photo source
by Stevie (AP Biology)
Not half bad? How can a disease be “not half bad”? Well, in a way, sickle cell anemia isn’t “half bad” at all! Sickle cell anemia is a disorder of the red blood cells that mainly occurs in African countries. It’s a genetic disorder where a person’s red blood cells are misshapen and do not efficiently carry oxygen throughout the body. It is a recessive condition which means a person must inherit only the recessive alleles (or genes) that code for their red blood cells to have this deformity.
The hemoglobin on the red blood cells does not properly deliver oxygen to other parts of the body, so someone who has this disorder will have multiple health problems and a much shorter lifespan. Someone who has hybrid (both dominant and recessive) alleles has red blood cells with mixed (or half!) sickle cells along with normal cells and will exhibit only minor health problems.
So how is sickle cell anemia only half bad? Well, a very deadly epidemic known as malaria has been sweeping Africa for thousands of years. It is caused by a parasite and it works by infecting the blood cells of its host. But, the amazing thing is that it cannot infect sickle cells. So if you have sickle cells you can’t get malaria! But, what does it matter if they can’t get malaria when they’re lifespan might only be a little bit longer with anemia?
The phenomenon lies in the hybrids (people with both the dominant and recessive alleles). Since they have sickle cells, malaria cannot infect them! Even better, since they also have normal blood cells, they are generally fairly healthy.
This phenomenon is referred to as heterozygote advantage (the hybrid allele combinations are called heterozygous), meaning that the heterozygous individual is more apt to survive than individuals with either the only dominant or only recessive allele combinations.
Confused? There’s a whole lot of confusing vocabulary in this post. If you are, just check the source. It really accurately defines everything and helps you to understand the specifics.
Can you find any other diseases or disorders that have this heterozygote advantage?
Do you have any unanswered questions about this concept or any comments about the condition itself?
December 15th, 2007 at 10:16 pm
thats really cool, i always thought that sickle cell anemia was a killer disease and nothing else. Thats great that it can prevent malaria, a huge killer. About how much longer can you live with sickle cells compared to malaria?
December 15th, 2007 at 11:34 pm
Hmm this is pretty interesting. I was a little bit lost when reading the posts but that website did help me get a better understanding. So basically, there are plusses and minusses to gettin sickle cell anemia?? Another thing is why risk getting this disease, and why can’t we just give medicine to the country of Africa to help prevent BOTH diseases? That seems like the most logical thing to do in my mind…nice post Stevie!
December 16th, 2007 at 2:20 pm
ive heard of this before! i mean i familiar with the word anemic cause my mom is. and she explained it as not having enough white blood cells so she always had to make sure when doctors drew blood to be careful. and she could never give blood cause she is anemic. but now if sickle cell prevents malaria….why dont they try and use it more offten?
December 16th, 2007 at 7:02 pm
This is pretty amazing! A disease that may be negative could actually become positive. In biology organisms always adapt and survive or die. This is a current example of how an organism can adapt to survive a deadly disease like malaria. Great post!
December 16th, 2007 at 7:57 pm
Like the questions guys!
Steven: Potentially, with the proper medical treatment, a fortunate individual could live an almost normal and semi-healthy, full lifetime. Most victims though in 3rd world countries, do not have the proper medical treatment and can only be expected to live 20 to 30 years.
http://www.kidshealth.org/teen/diseases_conditions/genetic/sickle_cell_anemia.html
Malaria, however, can kill in as little as about 2 weeks of contracting the illness.
Danny: Yes, there are advantages and disadvantages to both conditions, but persoanlly I’d rather have anemia! The only issue with African countries is though that alot of these victims do not necessarily have the healthcare available to survive for as long unfortunately.
Kristen: Well, since it is an inherited disorder, it would take a 10’s of millions of doctors altering the genetic sequences that code for hybrid sickle cell amemia in millions of 3rd world country patients. Good idea, but slightly impossible.
Thanks for the questions! Hope I helped
December 16th, 2007 at 8:42 pm
This is really cool how some of the people who have sickle cell anemia have an advantage the people that dont. I have one question though. Are Mosquitoes the only thing that can carry malaria?
December 16th, 2007 at 9:00 pm
Hank, I looked up malaria in depth on the CDC website, and it looks like only mosquitos carry malaria.
http://www.cdc.gov/malaria/
December 16th, 2007 at 9:16 pm
Now I know this may sound stupid but I read the article but I still do not understand why in the world would malaria not attack sicle cells? Is it because the viruse might think that was not a cell at all or was it because the immune system of a person with sikled cell might have given up on the other dieses and just attacked malaria?
December 16th, 2007 at 10:00 pm
Here is a website that may clear up some confusion.
http://www.labtestsonline.org/understanding/conditions/sickle.html
December 16th, 2007 at 11:30 pm
Well does if cickle cell anemia keeps oxygen from getting to certain parts of the body wouldnt they have respitory problems.
http://www.whfhhc.com/Diabetes/28416.htm
I found a good website that has info on diabetes that talkes about heterozygote advantage on diabetes. Its pretty interesting.
December 16th, 2007 at 11:52 pm
Haha, no Morgan you’re fine! When I wrote the post I didn’t know that you guys hadn’t gone over this kind of stuff in class. The malaria parasite does not recognize the sickle cells as healthy cells to attack, so if it can’t find a healthy red blood cell to infect it will just die and be expelled from the body. I’m really sorry, I also should have explained that some other white blood cells that fight off infection can also be infected by sickle cell anemia and therefore do not function to fight off infection. My mistake. Does that help at all?
February 19th, 2008 at 5:42 pm
wow still sickle cell anemia is a scary disease but not that bead huh! never though of it that way before. well i still believe it to be very scary to some, my friend has it and wow she is in pain so i dont know if i believe it to be ‘not half bad’ come on if you knew someone with it you would see there pain.