Why Do People Have Different Blood Types?

People have different blood types because of special markers on their red blood cells. These markers are like invisible stickers that tell the body, 'This is one of us!' or 'Watch out, this isn't one of us!' If someone has a marker your body doesn’t recognize, it might attack them! That's why some people can give blood to others, and some can't.

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Examples

If you have type A blood, your body will accept donations from people with A or O blood, but not B or AB.
A person with type AB can receive blood from anyone, making them the universal recipient.
Type O is called the universal donor because it doesn’t have any antigens that other blood types might attack.

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Categories: Biology · blood,genetics,immune system