Biology Question #719

Cynthia, a 35 year old female from Chilliwack, Canada asks on March 23, 2002,

IF my blood type is A negative what are my parents' blood types? What does it mean to have negative blood?

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The answer

Barry Shell answered on March 23, 2002

"Negative" refers to a blood factor called Rh. Some time ago, while studying Rhesus Monkeys' blood, scientists discovered a particular protein contained in the blood. Some people have it and some don't. Those that have it are called Rh positive (Rh stands for "Rhesus"). If you don't have the monkey protein you are Rh negative. If both parents are Rh negative you will be Rh negative yourself. It's possible for both parents to be Rh positive, but have received alleles for Rh negative, and if both negatives match up at inception, the child could be Rh negative, even though both parents are Rh positive. This is explained nicely at Paternity Angel.

For type A, both your parents would have had to be type A or one could have been type A and one type O. It's impossible to say which one.

Erin answered on November 2, 2002

Actually, in order for a child to be type A, the parents could be several different types. The only combinations of parents that could not make an A child are two O parents (which can only be expressed genetically as OO), or two B parents where the B is the only factor expressed (that is, BB not BO), or a B parent (BB) and an A parent (AA), or a B parent (BB) and an A parent (AO).

If you are a type A, it means that you are either AO or AA, depending on what was given to you by your parents. In my family, for example, my dad is type A, my mom is type B, my sister is type O, my brother is type B, and I'm type A which means that the genetic profile we have is: dad: AO (donated an O to my sister, an O to my brother, and an A to me) mom: BO (donated an O to my sister, a B to my brother, and an O to me) sister: OO, brother: BO, me: AO

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