DNA Day experts answer your questions about blood types

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How are DNA and Blood Types related?

Genetics of blood type - blood types are the result of proteins on the surface of blood cells, different types express different proteins, and these proteins are the result of different alleles of the same gene. One gene, two alleles, and either one, the other, or both, of the proteins are expressed. The really cool thing to me, as a geneticist, is that this system is then modified by another - the Rh factor. This factor is coded for by a second gene. Almost all of biology is like this - very, very few genes function in isolation. Almost all of biology is what we call "complex" a function of many genes acting together. Even eye color, which we often think of as being simple - one gene two alleles - is controlled by a dozen or more genes. This complexity is why my wife has green eyes, I have blue, and my daughter has blue - but a slightly different shade of blue. Complex.

- Answer provided by Dr. Thomas Merritt

Do children have to be the same blood type as their parents?

This is a very interesting question and it is hard to answer without higher level biology knowledge of blood types. But in general kids do not have to be the same blood type as their parents (for example, my mom is blood type A, my dad is blood type B, and I am blood type AB). However, it gets much more complex than that because we get two alleles for blood type, one from our mother and one from our father. So whichever blood type we have can only be a combination of the blood type of our parents. The reason why it gets so complicated is that there could be several combinations of blood types of the kids based on the blood type of the parents. So I will give you a brief general description: Blood type A can have the genetic alleles AA or Ai, Blood type B can have BB or Bi, Blood Type O can only be ii. Knowing which combination of alleles the children can have requires knowledge of Mendelian genetics and hybrid crosses (which I won't go into, unless you would like me to). Hope that answered your question!

- Answer provided by Harman Sawhney

If a mother's blood group is B+ and a father is B- is it ok for the baby to be A+ ?

Each person carries two copies (alleles) of the gene that determines ABO blood type. - if a person has two O alleles, they are blood group O - if a person has either two A alleles or one A and one O, they are blood group A - if a person has either two B alleles or one B and one O, they are blood group B - if a person has one A allele and one B allele, they are blood group AB As you can see, if both of a baby's parents are blood group B, then they can carry only B and O alleles, so all of their children should be either blood group B or blood group O - not group A! The + or - in someone's blood group refers to presence or absence of the Rhesus antigen. This gene has two alleles. - if a person has two + alleles, or one + and one -, they are Rh+ - if a person has two - alleles, they are Rh- So the baby in your question could have gotten a + allele from its mother, and then it would be Rh+ even if it got a - allele from its father. I hope this helps

- Answer provided by Stephanie Vogt

In terms of blood types, if I have an O type father, an A type mother, and an O type brother, am I more likely to be A type, O type, or is it impossible to determine. If it cannot be determined by that information alone, is it possible to determine it in reference to other genes, I mean, is blood type linked to other genetic alleles?

It would depend on whether your mother has 2 copies of the A gene or 1. That could be tested for genetically.

- Answer provided by Dr. Paul Gordon


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