Sickle-Cell Anemia isn’t Half-bad!

2010/01/25
By Stevie
photo by trebol-a

photo by trebol-a

This post was originally published on December 16, 2007.

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.

photo by PEIR

photo by PEIR

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?

  • Amy

    Thalassemia is another disease that has the heterozygote advantage. This disease is very similar to sickle-cell and it also prevents malaria in heterozygotes. This disease is caused by a mutation and it causes the body to have fewer red blood cells than normal and less hemoglobin. This disease can be deadly at an early age, but in the case of a heterozygote, it can be left untreated, have blood transfusions needed, or just eating healthy. Sickle-cell is found in people of African ancestry, while thalassemia is mostly in people with Italian, Greek, Middle Eastern, southern Asian and African ancestry.
    Here are two sites that I got the above information from:
    http://www.bookrags.com/research/heterozygote-advantage-gen-02/
    http://www.mayoclinic.com/health/thalassemia/DS00905

  • Geoffrey

    This is a very interesting post. I have done a little independent research and I have found out that there are more diseases that have this heterozygous advantage. Two examples of these diseases include thalassemia, which is another hemoglobin disorder that is most commonly found in areas bordering the Mediterranean Sea. Much like sickle cell heterozygotes for this disease are immune to malaria. One more example is a deficiency of the enzyme glucose-6-phosphate, this is found in similar regions as thalassemia; females with a heterozygous form of this disease are also resistant to malaria. I got this information at http://www.encyclopedia.com/doc/1G2-3406500137.html
    Also in my research I found that having the heterozygous form of sickle cell anemia suffer from similar symptoms of people with normal sickle cell anemia when subjected to low blood pressure situations such as high elevation. I got this information at http://chroma.gs.washington.edu/outreach/genetics/sickle/sickle-back.html

  • Jack

    After reading this post, I decided to check out how many heterozygote advantages actually exist out in the world. I found a PLoS ONE post about heterozygote advantages that exist in sheep, but the information was a little hard to digest. Maybe someone else can understand it.
    http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0000125
    I later found another site that explains three more examples of heterozygote advantages, including a gene that exists in flies. This gene gave flies improved viability, but it made them very weak. When a fly had a gene combination that included this viability allele and a regular allele, the fly was slightly weak but had improved viability. The advantages have outweighed the disadvantages though, so the viability allele has spread through fly populations. The site also includes information about how having one cystic fibrosis allele can prevent death from dehydration diseases like cholera. Last on the site is the debate about wether or not Tay-Sachs disease has a heterozygote advantage in preventing tuberculosis.
    http://en.allexperts.com/e/h/he/heterozygote_advantage.htm

  • http://scionlineproject.blogspot.com Michael S

    According to my independent research, an example of another heterozygous advantage [ http://www.plosone.org/article/info:doi%2F10.1371%2Fjournal.pone.0000125 ] is Tay Sachs disease [ http://www.ninds.nih.gov/disorders/taysachs/taysachs.htm ] . This disease causes lipids and a fatty substance called ganglioside to build up in the brain’s nerves and tissue cells. It is common among European Jews and in infants, who usually dieby age four even with intense treatment.
    The horrible effects of Tay Sachs disease are becoming blind, deaf, and they are unable to swallow. After having the disease for a while you paralysis takes place. People diagnosed with the disease also get red spots in their eyes.
    To tell if people have the disease a blood test is issued.
    In order to get the disease both your parents must have the mutation that causes the disease.
    Tay Sachs disease is considered a heterozygous advantage because it can aid in the prevention of Tuberculosis [ http://www.news-medical.net/health/Tay-Sachs-Disease-Society-and-Culture.aspx ]

    If you want more information on the disease check out: http://www-personal.umd.umich.edu/~jcthomas/JCTHOMAS/1997%20Case%20Studies/S.%20Bergeron.html

  • Sam

    This post was very interesting because it explained both the positive and negative side of Sickle Cell Anemia. The question at the end encouraged me to do further research and try to find other diseases that have the same heterozygote advantage. After looking on many websites I found the same disease that was posted above, Thalassemia. This disease is similar to sickle cell anemia because it is a malfunction with the red blood cells. Either there are not enough red blood cells or there isn’t enough hemoglobin in the red blood cells which effects the oxygen flow. This disease is inherited from the parents of the offspring. There are four forms of this disease called Silent Carrier State, Alpha Thalassemia Trait,Hemoglobin H Disease, Alpha Thalassemia Major. The first listed had one affected gene, the second has two affected genes, the third has three affected genes and the fourth has four affected genes.
    My information was found at these websites:
    http://www.labtestsonline.org/understanding/conditions/thalassemia-2.html
    http://www.nhlbi.nih.gov/health/dci/Diseases/Thalassemia/Thalassemia_WhatIs.html

  • Carl

    Like Geoffrey, I have done a little independent research about this very interesting topic. I came across this very helpful website http://en.allexperts.com/e/h/he/heterozygote_advantage.htm. In this article it explains the advantages of the heterozygote advantages with certain diseases. One example is with cystic fibrosis. This trait is a recessive trait which affects the lungs, sweat glands and the digestive system. This is caused by a problem with the CFTR protein. Although this disease can cause sterility, it also prevents death caused by the loss of bodily fluids, sometimes caused by cholera. People with this disease are usually of European decent.
    Another disease with advantages as a heterozygote is Tay-Sachs. This disease starts to take effect during the stage of infancy and causes mental retardation. This is very dominant amongst certain Jewish populations. In some studies, this disease has shown to prevent Tuberculosis.

  • Vincent

    This post is very interesting. People gain an advantage from having the sickle cell trait when exposed to malaria. Other than that the sickle cell trait can cause minor complications.

    http://www.cdc.gov/features/sicklecell/

    Complications can occur at high altitudes, increased pressure, low oxygen levels, or when dehydrated. Sickle cell anemia is most common in Africa, South America, Central America, Saudi Arabia, India, turkey, greece and Italy. Sickle cell anemia can be cured with a bone marrow transplant, but the surgery can be fatal. Sickle cell anemia can cause pain when sickle cells clog up blood vessels. People with sickle cell anemia can also be more prone to more diseases like influenza.

    People with Sickle cell anemia are less likely to get malaria, and less likely to die from it. But they are not completely protected from malaria.

  • Jesse

    This topic and post is very interesting. I never knew that having a deformed cell could also have a positive effect on you if you had malaria. This disease is also very common to the African-American population which caught my attention because in Africa they have a better chance of getting sickle-cell which also meant that they have a better chance of catching the disease of malaria because of the cleanliness in the continent.

    Another type of advantage is: http://ec.europa.eu/research/health/infectious-diseases/emerging-epidemics/projects/101_en.html

    This is a disease I found that is usually found in poultry. It is a kind of strep throat but it has a positive side where if you recieved an H5N1 Influenza it would not affect you at all. A disadvantage would be though that if you tried to have the Avian Influenza you could not take a vaccine until you are at the age of 18 because your immune system could not break down the supplements in the vaccine.

  • Matt C.

    Mike I will have to disagree with your information. When I did my research I found that Tay-Sachs disease may have advantages but it is not proven http://encyclopedia.stateuniversity.com/pages/21749/Tay-Sachs-disease.html.

  • Mike S

    Matt C.- My first question to you is your resource credible? If your resource is credible it states that:
    “Being a Tay-Sachs carrier may serve as a form of protection against tuberculosis. TB’s prevalence in the European Jewish population was very high, in part because Jews were forced to live in crowded conditions. However, several statistical studies have demonstrated that grandparents of Tay-Sachs carriers (who are more likely to have been carriers themselves) died proportionally from the same causes as non-carriers.” [http://encyclopedia.stateuniversity.com/pages/21749/Tay-Sachs-disease.html]

  • http://ashleysebesan.edublogs.org/2010/02/23/thing-4-commenting-on-blogs/ Thing 4: Commenting on Blogs | Living & Learning

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  • Vasiliki

    Another disease (mentioned above) with a heterozygote advantage is Tay-Sachs. Patients with this have a “Cherry red” spot in the back of their eyes called the retina. This is caused by an insufficient amount of an enzyme called hexosaminidase A. Patients of Tay-Sachs could test if they have this by a blood test that measures Hexosaminidase A activity. http://encyclopedia.stateuniversity.com/pages/21749/Tay-Sachs-disease.html

  • http://www.nature.com/nm/journal/v1/n7/abs/nm0795-703.html Jong

    Another heterozygous advantage is Cystic Fibrosis, a recessive hereditary disease of the lungs. This disease causes bronchitis, mucus on the lungs, inflamation of nasals, fatigue, asthma, liver inflammation, and other serious symptoms. Yet when the disease becomes heterozygote it is scientifically proven to protect the carrier or the diseased one with a much stronger resistance of cholera, tuberculosis, and/or asthma. So in other words, the cystic fibrosis could intervene with it’s original symptoms and instead of weaking, it could strengthen the defensive immune system for common lung diseases.

    Source
    http://www.cystic-fibrosis-symptom.com/symptoms.htm
    http://www.nature.com/nm/journal/v1/n7/abs/nm0795-703.html

  • http://saddlebredrescue.com Erin

    Great post! Another disease with the heterozygote advantage is Cystic Fibrosis. It is a disease that infects the lungs, causing large amounts of sticky mucus to build up in the pancreas as well. In the lungs it can block airways and make it difficult to breathe. If the pancreas is infected the digestive track can be clogged and digestion stopped. Although people with cystic fibrosis have a shorter life expectancy than normal, as treatments improve the life expectancy is rising. Also the earlier you get treatment the longer you will live. Symptoms of cystic fibrosis is salty tasting skin, wheezing, coughing, and short breath, excessive appetite but little weight gain. You can be tested from a sweat test or prenatal screening, or newborn screening.
    http://www.lungusa.org/lung-disease/cystic-fibrosis/symptoms-diagnosis-and.html

  • Deanna

    Your body requires fitness to survive and have offspring. Heterozygote advantage is the superior fitness often seen in hybrids. A heterozygote is an organism with two different allies, one from each parent. A heterozygous is for a particular gene, which usually can help you benefit from a disease. To acquire this trait your body needs to undergo the process of inbreeding. Inbreeding is the mating of closely related organisms. By doing this the number of heterozygous individuals increases. The copies of the DNA are identical, causing the new offspring to be heterozygous. However, there are also side effects. These side effects are slower growth, less resistant to certain diseases, and other signs of decreased fitness. When your body undergoes these symptoms this is called inbreeding depression. The site I got my information on was: http://www.highbeam.com/doc/1G2-3406500137.html.

  • Michael L.

    I really liked this post. I didn’t know that sickle-cell anemia was mostly a disease found in Africa. I did however find a disorder that mostly effects the caucasian population, it is called cystic fibrosis. Cystic fibrosis is a very serious and usually death causing disorder. This disorder causes the body to produce an excess amount of mucus that is very thick. The problem with this kind of mucus is that it does not flow through organs easily witch causes clogging witch is a serious problem.In the same way as sickle-cell anemia it is inherited and can be prevented by a heterozygous advantage.

    http://kidshealth.org/teen/diseases_conditions/digestive/cystic_fibrosis.html
    http://www.ionchannels.org/showabstract.php?pmid=1724059

  • victor

    Cool post! When doing research on deseases that can benefit a human body I was unable to find much. However after thinking a bit more, I came to the conclusion that common deseases such as colds can make you less vonarble to other deseases. This is not due to the cold it’s selfe but to the reaction your body has due to the cold. One of the reactions you body has when it detects a cold is nasal congestion, which helps keep other viruses away. Altough many do not apreciate nasal congestions, it is essential when it comes to keeping your body healthy. Here is some more information on nasal congestion. http://www.entnet.org/HealthInformation/stuffyNose.cfm

  • http://mmannpcs.edublogs.org/2010/06/08/reading-the-blogs-of-other/ Reading the blogs of others | Just Connect

    [...] Sickle-Cell Anemia Isn’t Half-Bad – I wanted to see how a high school biology teacher could use a blog with her class, providing provocative information in a visually interesting way, and how her students responded to her question, and what they had to know in order to explore the topic further. [...]

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  • http://never2late.edublogs.org/2010/06/10/thing-4-response-to-exploratory-reading-and-questions/ Thing 4: Response to Exploratory Reading and Questions | Principal 2.0

    [...] kids may be using all sorts of technology, but they may not be using it to its best advantage.  Sickle-Cell Anemia isn’t Half-bad! makes a fine template for how kids might blog in order to construct and share knowledge for their [...]

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    [...] Sickle-Cell Anemia isn’t Half-bad!:  This class’s Extreme Biology blog in general, and this post and its responses in particular, blow away the idea that students might be at all complacent if left to their own devices to simply blog away on academic matters.  No “Nice post!” responses here–students responded to what they read by going out and doing further research on their own, prompted by their own curiosity generated by their classmate’s post. [...]

  • http://lwtodd67.edublogs.org/2010/06/26/thing-4blogging-styles/ Thing 4:Blogging Styles | web 2.0 learning

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    [...] comments and posts by students were quite striking especially site on sickle cell anemia which is actually about heterozygote advantage.  The original post was entertaining and [...]

  • Kenny

    This was a very informative blog. I have a friend who has sickle-cell anemia and I know of the struggles that she goes through as far as health issues are concerned. She often has been hospitalized for various reasons some more serious than others. In this post there was essential information in it that gave me a better understanding about Sickle-Cell and why people with it have the episodes that they do.

  • GLEN

    Hi, I’m Glen, a 46 yr old sickle cell anemic. Married to a beautiful and wonderful woman who has given me
    3 handsome men they are 22, 21, and 13 years of age. Sickle cell anemia is more than half BAD. I deal with
    pain every day and live with it without complaint. It is more than half BAD when you go to the hostpital and
    the Doctor enters the room and asks me how long have I had Sickle Cell Disease, that when I get very angry.
    It does not help when the hospital think you are there to get a fix. I do every thing I’m suppose to do. I go to
    my doctors appointment, I take my medicine, and eat healthy. So I do hope you see some good things. As
    for me I must take Sickle Cell Anemia very serious until there is a CURE for children and Adults.!

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