MadSci Network: Genetics

Re: father blood group is A+ mother Blood Group B+ daughter blood group O+

Date: Mon Apr 19 14:39:53 1999
Posted By: David Beck, MadSci Admin
Area of science: Genetics
ID: 924476061.Ge

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 

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 

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 

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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