|MadSci Network: Genetics|
The answer is really simple. There are two copies of all the genes in the body, these two copies are not necassarily the same. Think about a hard cover book and a soft cover book. It can be the same book, but a hard cover book is different than a soft cover book. Now when we consider blood type there are two sets of genes, blood type A,B,AB, or O and Rh factor + or -. I will deal with Rh factor first because it is simpler. Mom is Rh +, and Dad is Rh +. What does it mean to be Rh +. Someone who is Rh + has an Rh gene that works, someone who is Rh - doesn't have an Rh gene that works. So an Rh + can either have two copies of the Rh gene that work (++) or only one gene that works (+-). But an Rh - can NOT have a copy of an Rh gene that works (--). Now when a Mom and Dad have a baby the each contribute ONE copy of their genes to the baby. If Dad or Mom is Rh+ then they can contribute either a + or a - to the baby if the are +-. If they are ++ they can only contribute a + gene. In order for the baby to be + the baby only needs to receive one + copy. So from the information provide that Mom, Dad, and Child are + it can not be determined whether they are +- or ++ only that none of them are --. Now blood group. This is a little more complicated because there are three different kinds of the blood group gene. There are two copies that work A and B, and a third copy that doesn't work O. So there are four different blood types: A, B, AB, and O Now in order to be each of these blood types you can have any combination of the following: Type of blood Type of gene copies A AA or AO B BB or BO AB AB only O OO only Now since Dad is A, and Mom is B, and the child is O we can determine the type of gene copies each person in must have. Dad is AO Mom is BO Child is OO So both Mom and Dad contributed the O copy of there blood group genes to the child. Since Dad is AO and Mom is BO then we know for sure that they can have children with any of the following blood groups: A Dad gives A copy, Mom O copy B Dad gives O copy, Mom B copy AB Dad gives A copy, Mom B copy O Dad gives O copy, Mom O copy Besides it is cool to have the O blood type. Blood type O is called the universal donot. You can give blood to anyone that is A+, B+, AB+ or O+. Mom can only give blood to someone who is B+ or AB+, and Dad can only give blood to someone A+ or AB+. Hope this helps, David Beck MadSci Admin
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