I like dabbling with my family tree, looking at the names and places, wishing I knew more about the stories of everyone who contributed to who I am.

I’ve had Ancestry.com and MyHeritage subscriptions, and I’ve purchased DNA kits from both 23andMe and Ancestry.com. 23andMe told me about some of my physical traits and health risks (read that old post here), and once in a while, both services update their ancestry markers and send out an update.

Once you receive your DNA results, both services let you download your raw DNA data. But … what can you do with it? For years, that answer was pretty much nothing.

But now! AI! Super computers! So naturally, I fed my DNA information into Claude (an AI provider) for analysis. And you’ll never believe what I uncovered!?

I’m carrying two copies of the Duffy null variant (I have TT at rs2814778).

Why is that fascinating?

That variant means I’m immune to Plasmodium vivax malaria.

I’m a pale-skinned, light-haired, Canadian with European roots (mostly Dutch, Irish, with bits of English, Scottish, and German) and that Duffy null variant is common in people of African descent. My DNA shows that I have a West African ancestor on my mother’s side, about 4-8 generations ago, who likely passed along the trait.

Malaria Resistance?

Yes, I apparently have inherited a likely 100% immunity to Plasmodium vivax malaria, which is one of 5 strains of malaria. It’s the strain that is common in southeast Asia, Latin America, and in parts of Africa. It’s less deadly than the falciparum form, which is common in sub-Saharan Africa and much more deadly. I’m not immune to that one at all.

This strain of Malaria, Plasmodium vivax, enters the Duffy Antigen receptor on red blood cells to invade your system. This variant I have means I don’t express this receptor so this malaria parasite can’t enter my red blood cells.

It is actually a great example of ‘survival of the fittest’ evolution. Due to their immunity from this malaria strain, the people of West Africa who carried this variant survived and had more children, and now this variant has reached almost 100% frequency in some African populations.

This Duffy null variant usually goes hand in hand with lower neutrophil counts. I wonder if that is true for me and if that would have been evident in any of my cancer treatment monitoring. It’s called Duffy-null associated neutrophil count (DANC). (More information on this here.)

Genetics

But wait. I said I had TWO copies. I have TT (at rs2814778) – homozygous TT – of the Duffy null variant, which is quite rare in someone with primarily European ancestry. That means I’ve inherited it twice.

That means both of my parents carried this variant.

My DNA structure on these services have always told me that I have 1-2% Nigerian or West African DNA coming from my mother’s side. My Dad’s side of the family tree shows up as 100% European. The African (or even Asian) either completed diluted, over many generations, or the genetic variant was acquired from some other population in my father’s ancestry.

I had first assumed the Duffy null variant must be dominant for it to persist across these generations, but it isn’t. It is recessive!

Let me explain a bit more about how this works. There are three possible genotypes:

CC (normal):

• Expresses Duffy antigen on red blood cells
• Fully susceptible to P. vivax malaria

CT (heterozygous – one copy):

• Expresses SOME Duffy antigen (reduced levels)
• Partial resistance to malaria (lower parasite density)
• Co-dominant – you see effects of both alleles

TT (homozygous – two copies – ME):

• Expresses NO Duffy antigen
• Complete resistance to P. vivax malaria
• Recessive – needs both copies for full effect

The Duffy null variant survived through generations NOT because it’s dominant, but because:

1. It’s on a simple chromosome – just gets passed along

• Even if you’re CT (one copy), you still carry the T
• You can pass that T to your children
• It silently travels through generations

2. Natural selection in malaria zones

• In Africa, having even one T (CT) gives a survival advantage
• People with TT had the best survival
• People with CT had moderate survival
• People with CC died more often from malaria
• The variant increased in frequency due to selection pressure

3. Random inheritance – 50/50 chance

• Every time someone with the T allele has a child, there’s a 50% chance they pass it on
• Even if it doesn’t “show” (because they’re CT), it’s still there
• It can resurface generations later when two CT people marry

That means my parents are either CT or TT, but for me to be TT, neither of them can be CC. If one, or both of them, are CT (likely), rather than TT, my siblings may not have inherited this trait. Without testing some of my immediate family members’ DNA, there is no other way to tell.

Could all of this have been a mistake? I analyzed my raw DNA results from both services and they both show this double TT Duffy null variant marker, so I think it’s legit!

Who is the African ancestor that shows up on my maternal side?

I feel like I will probably never know. I can see through these ancestry tools that a few relatives have also done DNA testing. Comparing my ancestry with theirs, I can filter the lines of my family tree that show African ancestry, and those that don’t. So I can estimate which branch of my family tree has descended from this person. But then what?

I have found one ancestor described as “mulatto” but only in one census (Canada 1901), and no one else in their family is, so I expect it was a mistake. Other than that, I have no other clues that I can act on.

What can I do with this information?

Probably nothing, except blog about it, since there isn’t Malaria in Canada, this is pretty irrelevant. Although I am likely travelling to Asia later this year (work trip) for the first time! More on that later.