Paternity DNA testing

When we look at parental DNA testing for maternity and paternity—say if the mother is AB and the father is CD—is it true they could produce four different offspring combinations by taking one allele from the mother and one from the father: AC, AD, BD, and BC?

Does this imply the first allele at the locus will always belong to the mother and the second to the father?

For example:

Mother Father Child
AB CD AC
10,11 13,15 10,13

An allele is simply an alternative form of a gene located at a specific position on a specific chromosome.

Based on that definition (which, frankly, is just a translation from English)—would the child's combination of 10,13 be considered identical to 13,10? In other words, are the alleles 10,13 and 13,10 actually the exact same thing? Is the position 10,13 effectively the same as position 13,10?....

I’m not entirely sure if I’ve phrased this perfectly—I really hope someone can make sense of what I'm getting at here...

Since nobody seems to have responded yet, I am going to rephrase my question—again.

In DNA paternity and maternity testing, if the mother is AB and the father is CD, they could theoretically produce four different offspring combinations by taking one allele from each parent—specifically AC, AD, BD, or BC, right?

Does this imply that the first allele at a specific locus will always originate from the mother, while the second comes from the father?

For example:

Mother Father Child
AB CD AC
10,11 13,15 10,13

Now, suppose the position at the D8S1179 locus is, say, 13, 10. That would mean the 13 comes from the father and the 10 from the mother—which doesn't fit the four possible combinations listed above! It would look like a CA combination, and frankly, after scouring the internet, I haven't found any mention of a "CA" variant among standard offspring combinations.

Furthermore—and I'm not entirely sure if this matters—does the child's sex play any role here? For instance, would girls always have combinations where the first allele is maternal and the second is paternal, or is there no connection between gender and these genetic markers whatsoever?

When looking at an analysis involving 15 loci, roughly how many loci would typically show the father's allele in the first position? I've noticed in several online reports that, more often than not, the majority of loci start with the mother's allele.

To illustrate—I saw one online report where out of 10 analyzed loci, only two actually started with the father's allele.

I am assuming that in a case like the CA combination, we are talking about Genetic recombination.

That is how I read it in an English-language source.

Genetic recombination usually results in a partial recombination, or creation of combinations OFF alleles in chromosomes not present in either parent. Could this be interpreted in a DNA test as evidence that neither the mother nor the father is actually the biological parent?

An allele is simply an alternative form of a gene located at a specific position on a specific chromosome (my own translation of the term). Given that fact, is the position 10, 13 at the D8S1179 locus functionally identical to the position 13, 10?

Can anyone actually provide an answer to this?

I honestly have no idea what you're getting at here... do you truly believe a test can be manipulated, or are you suggesting certain genetic overlaps are technically "impossible"

well?🤔

I am not suggesting it is possible to rig the test—what, by bribing lab technicians or something?—nor am I even attempting that! My goal is simply to understand every single granular detail, including the specific methodology used to calculate the PI (paternity index). That is precisely what they are refusing to let me see—they won't provide an actual example of the calculation itself. Sure, you can find formulas online, but when I run the numbers myself using those formulas, they absolutely do not align with the results printed on my report.

I don't quite grasp what you mean by your question regarding "technical" discrepancies? Honestly, I have no idea if you have ever actually held a DNA maternity or paternity analysis result in your hands before. If you aren't from a medical background, it’s going to be difficult for you to wrap your head around this—and believe me, I have been digging through the internet trying to make sense of it all, but I haven't quite mastered everything yet, so I can only offer so much.

Furthermore, I am not asking about my own child—I don't have children—but rather due to certain circumstances I'm not prepared to disclose right now. I went for a DNA analysis alongside my legal parents, which confirmed paternity; however, I was never issued a maternity result showing that 99.9% certainty... and mind you, I requested and paid for both maternity and paternity testing!

Another matter that has genuinely rubbed me the wrong way is that on the very day they told me the results were ready for pickup, they issued me yet another invoice—this one featuring a completely different transaction ID and security code compared to the original report, which had already been paid in full on the day the samples were collected. It felt as though my credit card had been swiped twice: once during sample collection, and again just before I picked up the results.

When I confronted them, they claimed that's just how they operate—that they "void" a down payment, even though it wasn't even a down payment in any real sense because the service was paid for upfront in its entirety! They implied that for a full, court-admissible report, there would need to be additional fees, but I haven't even reached that stage yet. And frankly, why should I even bother asking for a seal verifying a forensic expert's signature when they won't even give me the basic information I'm looking for?

It strikes me as utterly illogical for a business to issue two separate invoices for one single service, complete with two different transaction IDs and two different security codes. What kind of company would intentionally void its own revenue? It makes zero sense. Consequently, I'm starting to suspect that someone else might have had their fingers in the cookie jar here—perhaps one of my parents—and I am even beginning to doubt whether the report I received is anything more than a surface-level version designed to keep me quiet while the "real" report is handed to someone else—clearly not for my eyes. At this rate, I will likely have to repeat the entire process anonymously in another country.

So, I am requesting that if anyone here possesses medical expertise—an area where my opinion is currently quite low—you please address the questions I have laid out above.

Angela Bailey7 said:Since nobody seems to have replied yet, I'll just try rephrasing my question...

If we're looking at DNA testing for maternity and paternity—say the mother is AB and the father is CD—could they have four different offspring combinations by taking one allele from each parent? Like AC, AD, BD, and BC?

Also, does that mean the first allele listed at a locus will always be from the mom and the second from the dad?

For example:

Mother Father Child
AB CD AC
10,11 13,15 10,13

So, if the position at a locus like D8S1179 shows 13, 10, that would mean the 13 comes from the dad and the 10 from the mom—which doesn't fit those four possible combinations I mentioned... and I couldn't find any mention of a "CA" combination when searching online.

From what I remember, if you have this:

Child Mother Father
10,13 10,11 13,15
BA BC AC

In this case, the mandatory allele the child *must* inherit from the father is 13—and the formula just for that specific STR locus, D8S1179, is PI=1/2a (where 'a' is the frequency of that allele within the specific population you're testing).

Basically, you look at the mandatory allele—you don't just assume the first one belongs to the mom! For instance, if you assume the mom is AA and the child is AB, then that B allele absolutely has to come from the biological father. If the alleged father doesn't carry that B allele—meaning there's no way he could have passed it down—and you rule out a mutation at that specific marker, then you can exclude him...

The formula specifically for that STR locus D8S1179 is PI=1/2a—where "a" represents the frequency of that specific allele within the particular population you are analyzing.

Now, how exactly does one arrive at that value for "a"—the allele frequency? Could you perhaps demonstrate the principle using some sort of hypothetical example?

And furthermore, is the formula for the second locus, D21S11, identical to the one I just mentioned?

So, essentially, you look at the mandatory allele—you don't just go in assuming the first one belongs to the mother. For instance, if you assume the mother is AA and the child is AB, then that B allele absolutely must have come from the biological father.

Okay, I follow that. What’s actually tripping me up—and this is where it gets messy—is that I was reading a presentation online which suggested that if a mother is AB (let's say 10, 15) and the father is CD (say 14, 16), they could produce four possible offspring combinations: AD, AC, BC, and BD—specifically (10,14), (10,16), (15,14), and (15,16). This seems to imply that the first allele always comes from the mother... and according to the logic in that presentation, a combination like CB (14,15) would be impossible because it isn't listed among those four possibilities! So, is BC (15,14) and CB (14,15) actually the exact same thing? In the case of BC, 15 is from the mother and 14 is from the father, but in the case of CB, 14 is from the father and 15 is from the mother. Based on that sentence in the online presentation, CB isn't listed as one of the four possible outcomes, and it's driving me crazy—it's just the swapping of numbers that is making my head spin... and this text below as well...

Given that fact, is the child's position at a locus like D8S1179 being 10, 13 identical to the position 13,10? I am struggling with this idea of a "specific position" on a chromosome—does 10,13 mean the same thing as 13,10 in that context? Do those numbers 10,13 represent that specific location? I don't know if I've explained what's bothering me clearly enough, since I'm certainly not a medical professional and I can't really provide a visual representation.

Genetic recombination usually results in a partial recombination, or creation of combinations OFF alleles in chromosomes not present in either parent. Could this be interpreted, if it occurred during DNA analysis, to mean that neither of the tested parents—neither the mother nor the father—are actually the biological parents of the individual?

If you are able to explain, perhaps with an example, what would actually constitute crossing-over? I was reading some texts in English and I'm not quite sure how we refer to it here in the States.

An allele is an alternative form of a gene located at a specific position on a specific chromosome (that's my own translation from the English).

Considering that fact, is the child's position at a locus such as D8S1179 being 10, 13 identical to the position 13,10? I'm hung up on this phrase "specific position on the chromosome"—does 10,13 mean the same thing as 13,10 in that sense? Assuming I've framed the question correctly, that is.

Regardless, thank you so much for this answer you wrote.

These frequencies are calculated at the population level—basically, based on the specific country where the people being tested live. There are pre-calculated tables created by specialists for this exact purpose. You then plug those values into formulas derived from the various combinations of maternal, paternal, and fetal alleles. So, regarding your question about whether the formula for the second locus, D21S11, is identical... it doesn't necessarily have to be! It all depends on which specific allele combinations you're looking at (there’s actually a table for that too)

As for genetic recombination—our term for it might be "crossing over"—that's when intertwined chromatids break and reconnect, allowing homologous chromosomes to swap genetic material. (This happens during meiosis I, specifically during prophase I)
The actual site where genetic recombination occurs is called a chiasma.

For anything else, you really ought to check with a specialist.🙂

Angela Bailey7 said:The formula just for that STR locus D8S1179 is PI=1/2a (where a is the frequency of that allele a within the specific population you are testing).

How do I arrive at that value for a—the allele frequency? Could you demonstrate the principle using a hypothetical example?

And is the formula for the second locus, D21S11, identical to the one above?

So, you look at the required allele (you don't assume the first one belongs to the mother). For instance, if you assume the mother is AA and the child is AB, then that B allele must come from the biological father.

Okay, that makes sense. What confuses me is that I read an online presentation stating that a mother AB (say, 10, 15) and a father CD (let's say 14, 16) could produce four possible offspring combinations: AD, AC, BC, and BD (10, 14) (10, 16) (15, 14) (15, 16)... which aligns with the idea that the first allele comes from the mother. According to that presentation, a combination like CB (14, 15) would be impossible because it isn't listed among those four. Is BC (15, 14) and CB (14, 15) actually the same thing? In the case of BC, 15 is from the mother and 14 is from the father; in the case of CB, 14 is from the father and 15 is from the mother. The fact that CB isn't listed as a possibility in that presentation is throwing me off. It’s just the switching of numbers that's confusing me... and this text below...

Given that, is the child's position at a locus like D8S1179 (10, 13) identical to D8S1179 (13, 10)? I am struggling with the term "specific position" on the chromosome. Does 10, 13 mean the same thing as 13, 10 in this context? Do the numbers 10, 13 represent that specific position? I'm not sure if I've explained my confusion clearly, as I don't have a medical background, so I can't really provide a visual.

Genetic recombination. Could this be interpreted, if it occurred during DNA analysis, as meaning that neither tested parent—neither the mother nor the father—is the biological parent of the individual?

If you can explain what would be considered crossing-over using an example—I was reading texts in English, so I'm not sure how we refer to it here?

An allele is an alternative form of a gene located at a specific position on a specific chromosome (my own translation from English).

Regarding that fact, is the child's position at a locus like D8S1179 (10, 13) identical to D8S1179 (13, 10)? I am questioning the term "specific position" on the chromosome. Is 10, 13 effectively the same as 13, 10? If I phrased the question correctly.

Anyway, thank you so much for this answer as well.

What is the damage for all this?

Look, there are actual pre-calculated tables for this stuff—prepared by professionals who deal with this all day long... can I just find those somewhere online? How do I actually get my hands on them?

So, regarding your question about whether the formula for the second locus, D21S11, is identical—well, not necessarily! It all hinges on which specific allele combinations you're looking at. (There’s a table for that too, obviously)... but are these tables even available on the web?

It feels incredibly frustrating to receive these PI index analysis results and then be completely shut out from the actual calculation methodology. I mean, it’s ridiculous—I’m essentially being forced to just take this percentage at face value without any way to understand the math behind it or replicate the lab's own results myself.

And one last thing—if you don't mind answering—I have one more question down below... please forgive me for badgering you with all these questions, but you're honestly the only person who has been able to give me a straight answer to what I'm actually asking.

An allele is simply an alternative form of a gene located at a specific position on a specific chromosome (that's my own translation from English).

Given that fact, would the child's position at a locus like D8S1179 being 10, 13 be considered identical to the position 13, 10 at D8S1179?

Jose Clark2 said:How much does this whole celebration cost?

I honestly don't follow the question—any lab out there will have their own price list... who exactly is looking for results here?

Look, Angela Bailey7, I won't go through his entire post, but I ran a DNA paternity test for my daughter and got a 98.9% match, which is more than enough for me. I don't need maternity testing because I am 100% certain she is mine 😛 but he—the biological father—went through the process by mailing a saliva sample to a lab in Canada via USPS. He didn't use a local clinic; it cost him about $250, and he'll send you the details via email. If you are truly dead set on repeating this, I can ask him exactly where he sent it, though I have the paperwork right here and it should specify the lab
In my opinion, don't just throw money away for nothing. I'll send you a private message if you want the info

Kate Jones said:Look, lady—and I’m not even going to bother quoting your entire post because we both know where this is going—I have a DNA paternity test for my daughter where the probability was 98.9%, so I actually know what I'm talking about here. I don't need a maternity test to prove anything because I am 100% certain she came from me 😛 but he (the biological father) did a test where he just mailed a saliva sample off to a lab in Canada via USPS. It wasn't some high-end clinical lab, just a standard one, and it cost about $250—check your email, they should have sent you the details. If it’s truly that vital for you to repeat the process, I can ask him exactly where he sent it; honestly, I have the paperwork right here and the lab info should be printed on it.
I mean, don't just throw your money away for nothing. I'll send you a DM if you want the info.

Are you being serious right now? You're telling me it's only $250... I was actually considering driving all the way down there myself, but I checked the Amtrak schedules a few days ago and there aren't any good routes... looks like either I was the first one to waste money on this, or someone else has been throwing cash out the window too...

I’m not following you. 🤔 Honestly, it’s straightforward: you order the kit, they ship it right to your door, you send the samples back to the lab, and then the results hit your inbox. The catch—if there is one—is that these tests aren't typically admissible in court because they lack specific judicial certification. Still, the accuracy is high.

Look, I don't really grasp all these numbers you're throwing around 😉 (though I respect the effort 😁), but if you decide to run it again, I can get you the exact details tomorrow on which lab to use and where to order from.

Look, it’s quite simple—I want to drive across the border to a lab in Vermont, drop off the samples myself, and be back home in Chicago before I know it... I don't see what the big deal is... Sure, it might be less of a headache to just send everything via FedEx, but I prefer being hands-on! And besides, I can't exactly hop on a train to get where I'm going because the rail lines heading toward the border are completely shut down right now...

I'm looking to get a paternity test done—father and son. Where can I find the cheapest option around here, and what kind of pricing are we talking about? Looking for some DNA lab recommendations in the US.