• Question: Why are there different types of blood?

    Asked by 534bera34 to Colin, John, Kevin, Shikha, Triona on 17 Nov 2014.
    • Photo: Tríona O'Connell

      Tríona O'Connell answered on 17 Nov 2014:

      There’s about 20 differnt blood groups (more than just the ABO / Rhesus D+/-). Some of them are proteins on the cell surface, others are sugars (ABO is a group based on sugar structures on the cell). Slight variants in the proteins or sugars often correspond to different groups.
      If the variants cause disease, they’re not likely to be sustained in a population. If the variants have no benefit or downside, they might also stay. If a variant has a benefit (eg. reduces the ability of a disease to get into your blood cells), then it sticks around in a population.
      So in essesence, some are useful, some don’t cause problems, and we have a lot of traits that are varied between us, blood groups are just another one.

    • Photo: Kevin Motherway

      Kevin Motherway answered on 17 Nov 2014:

      People always talk about “lock and key” mechanisms when it comes to disease. Humans are all the same species but we all have slight little differences that means that no one diease could wipe us all out. A good example is that many people from sub-sarahan suffer from sickle cell anemia, but that also gives them a relative immunity to malaria. In the USA it’ seen as a health problem in the Afican-American community, but it actually provides an evlutionary advantage to the same genetic popultaion living in sub-saharan Africa where malaria is a huge problem.

    • Photo: Shikha Sharma

      Shikha Sharma answered on 19 Nov 2014:

      Hi 534bera34,

      In 1900, Karl Landsteiner described the original blood types- A, B and O. Type of blood is totally dependent on the types of proteins, glycoproteins and glycolipids found on the surface of red blood cells(RBC). Generally, blood type or gene responsible for blood type is inherited. You know type A is the most ancient, and it existed before we human beings even evolved from its hominid ancestors. Type B is believed to have originated some 3.5 million years ago due to a genetic mutation which modified one of the sugars on RBC. The around 2.5 million years ago, again mutations occurred that reduced that sugar gene inactive, creating type O, which has neither the A or B version of the sugar. And then there is AB, which is covered with both A and B sugars.

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