Raising Boys

Blood–what’s your type? November 11, 2005

My husband and I picked up the results of the blood typing tests on our sons Dylan and Lennon at the clinic this afternoon and learned that Dylan is AB+ and Lennon is A+. That’s to be expected I guess because blood type is inherited and I’m AB+ while my husband believes (he’s not sure) he is B+.

We had the tests done on our children because we thought it would be handy information to have.

I wanted to learn more about blood types so I looked it up on the Internet and found out that a person has two blood alleles, one each from the biological parents. A tutorial on the University of Arizona biology project website said “an allele is one of several different forms of genetic information present in our DNA at a specific location on a specific chromosome.”

There are three different alleles for blood types: A, B, and O. It was Austrian scientist Karl Landsteiner who classified blood according to the distinct differences he found when he examined samples under a microscope.

Landsteiner observed two distinct chemical molecules present on the surface of the red blood cells. He labeled one molecule “A” and the other molecule “B.” If the red blood cell had only “A” molecules on it, that blood was called type A. If the red blood cell had only “B” molecules on it, that blood was called type B. If the red blood cell had a mixture of both molecules, that blood was called type AB. If the red blood cell had neither molecule, that blood was called type O.

Each one of us has two of the blood type alleles because we inherit one each from our biological parents. This pair of alleles in our DNA is called genotype. Our blood type alleles of A, B, and O produce a total of six different genotypes: AA, AB, AO, BB, BO, and OO.

A blood type test can determine if the A and B characteristics are present in the blood but it can’t determine the person’s exact genotype. In other words, the test can determine if the person is blood type A but it can’t determine if the person’s genotype is AA or AO. Both these combination result in blood type A. The genotype BB and BO also result in blood type B.

A blood type O can only result if both parents contribute the O allele to their children. A mother with AO blood type alleles, with blood type A, can contribute either the A or O allele to her child. A father with the BO blood type alleles, with blood type B, can contribute either the B or O allele to his son or daughter.

A blood type test result of AB or O is more informative as people with blood type AB could only have the A and B alleles and can contribute any of these to their children while those with blood type O could only have both O alleles and can only contribute the O allele to their kids.

Hence, if my husband is B+ and because my sons are A+ and AB+, his genotype could only be BO. In Dylan’s case, who is AB+, my husband contributed the B allele while I contributed the A allele. In Lennon’s case, who is A+, my husband contributed the O allele while I contributed the A allele. If my husband’s genotype had been BB, my sons could only have had blood types of AB (A allele from me and B allele from him) or B (B allele from me and B allele from him).

It’s also possible, though, that my husband’s blood type is A and his genotype is AA or AO. In Dylan’s case, he contributed the A allele while I contributed the B allele, and in Lennon’s case, he contributed the A allele while I contributed another A allele or he contributed the O allele and I contributed the A allele.