Blood Type

[darkerhorse]

The geographic distribution of blood types is shown here:
https://www.palomar.edu/anthro/vary/vary_3.htm

Is there any evidence that blood type is related to DNA inheritance?

For example, are we more likely to have inherited DNA (in general or in specific traits) from ancestors with our blood type?

I have the same blood type as my father and my paternal grandmother. My siblings have the same as my mother and paternal grandfather. Blood types of my maternal grandparents are unknown.

[MarcuccioV]

That's an interesting question. Both my parents were O-, and I as well. Grandparents (both sides) unknown...

[darkerhorse]

My blood type is relatively uncommon, while my Y haplogroup is relatively common.

The geographic concentration of my blood type (shown in the map linked above) coincides with the (reputed) geographic origin of my Y haplogroup. In other words, my blood type, though uncommon, is prevalent where my Y haplogroup is thought to have originated.


My blood type is the same as my father but different from my paternal grandfather (the Y haplogroup line).

So, it looks like there's really no correlation going on.

Make a question out of that, and answer it.

[parkergambino]

The genetics of inheritance of blood type are a bit more complex than some other traits. So it is hard to find a reference that simplifies the whole shebang without going into excessive details that are not essential for most genealogical research. This site covers the basics pretty well:
http://www.biology.arizona.edu/human_bi ... osses.html

My simplified, good-enough-for-high-school-biology (which I taught) primer:

There are two distinct loci on chromosomes (= 2 sets of alleles, or genes) for the two different traits. The alleles (genes) for the "A-B-O" system are located on chromosome #9. The alleles for the Rh factor (+ or -) are located on chromosome #1. Everyone receives two alleles of the ABO system (one from each parent) and two alleles for the Rh factor (one from each parent). These traits are inherited independently of each other. Both need to be taken into consideration for successful blood transfusions, etc.

In a sense, these gene products (antigen proteins), and reactions to them, can be thought of as cases of immune system allergic response. Ideally, if you create an antigen protein within your body, you would not be allergic to it. You would also not be allergic to it if it entered you body via a transfusion. But, in receiving a blood transfusion or organ transplant from someone with a different blood type (based on these genes), you might be receiving an incoming antigen not already present in your body, to which you are allergic. Serious consequences ensue.

The inheritance of Rh factor follows the rules of simple Mendelian inheritance: positive is dominant, meaning that the Rh antigen is produced, in both homozygous and heterozygous individuals. Negative is the recessive trait, producing no antigen, and must be homozygous for the recessive allele. Since the Rh negative individuals create no antigen, they can donate to recipients who are either positive or negative for Rh factor. (Irrelevant trivia detail: named "Rh" because first studied in Rhesus monkeys).

Things get complicated with the ABO system, which follows Mendelian rules, but in which there are three different allele variants (two dominant, one recessive), which can be combined to give six different genotypes. Type O is recessive, creating no antigen, and must be homozygous. Both A and B antigen genes are dominant ("co-dominant"), and are expressed if they are present. Type AB contains one dominant A antigen gene, and one dominant B antigen gene, so must be heterozygous. Type A can be either homozygous (two A antigen genes) or heterozygous (one dominant A antigen gene and one recessive O gene); type B can likewise be homozygous or heterozygous. The matrix of offspring possibilities gets complex, and I will defer to the website for further elucidation. Pedigree analysis of parental, and sometimes grandparental, generations can be used forensically for paternity tests. For example, in the simplest cases, a type O father cannot sire a type AB offspring, nor can a type AB father sire a type O offspring.

World-wide, the O allele is much more common than A or B, according to the original link above. I quibble with the way the site expresses allele frequencies worldwide: yes, the numbers 63% + 21% + 16% do indeed add up to 100%, but that is not really technically the equivalent of saying that 63% of people "share" the O allele. Nonetheless, we get the general idea. When looking at geographically distinct populations, the alleles are not evenly distributed. Broadly generalizing,the A allele is more common in northern Europeans than in Asians, the B allele more prominent in Asians than in Europeans. Neither allele is at all common in native South Americans. A painfully comprehensive table elaborating blood-type distribution data is found here:

https://en.wikipedia.org/wiki/Blood_typ ... by_country

Parker

[parkergambino]

I took a deep breath and reviewed this thread. There were the two initial questions, worth getting to. But first...

The ABO blood typing system was discovered and elaborated in the early part of the 20th century, so certainly no one before, let's say, 1900, had their blood type analyzed and reported. Because of the complexity of the 3-allele system (most Mendelian inheritance relies on there being just 2 possible alleles), it is within the realm of possibility that two parents (heterozygous A & heterozygous B) could have four children, one each of the four possible blood types: A, B, AB, and O. So, aside from paternity tests and their ilk, described in the previous post, I expect there to be little of use for investigating family genetic history that goes more than a couple of generations back from the present, or from the date of testing.

Regarding blood-type testing in the 21st century, reporting merely a type A allele (or B, or O) is a gross oversimplification of the reality of exactly how many genes are involved, and the number of mutations that have already been discovered amongst them. Although I don't think this has yet had major practical significance for managing blood transfusion compatibility and other health issues, as we gradually clarify the genetic nano-details, refinement of procedures and improvement of outcomes will surely follow. My understanding is that all of this complexity is of keen academic interest for researchers of evolutionary genetics, but not easy to share with genealogists in a meaningful or particularly relevant way. I doubt that these myriad genetic variations are covered by any standard DNA analysis kits made available by various commercial enterprises. (Caveat: I haven't done extensive investigation of all of these commercial products, especially of the health risk reporting protocols).
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To the questions.

Is there any evidence that blood type is related to DNA inheritance?
Blood type IS a manifestation of DNA inheritance and expression, so must be related to DNA inheritance.

For example, are we more likely to have inherited DNA (in general or in specific traits) from ancestors with our blood type?
Since the ABO system gives fluid and slippery inheritance results that are less straightforward than other Mendelian traits, I'm gonna say pretty much no. If we re-frame this question as whether there might be correlations betwen certain blood types and other ancestral traits, then maybe a bit, I would guess mostly with traits that are linked on the same chromosome (#9 in the case of ABO). My own take on all of this is that the evolutionary pressures associated with the origin of the ABO system are mostly irrelevant in 2023, and perhaps have been so for centuries. Therefore, patterns in the distribution and inheritance of these genes don't follow predictable trajectories; they are more randomly determined, perhaps accounted for by founder effect more than anything else. As such, they have some usefulness in tracing historic population-scale migrations.

Parker