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roxie60 - I took a 2nd look at the DLA-DRA data I have, and was able to get a bit further with it now, probably due to far less brain fog than the last time I checked them. Basically by "subtracting" the alleles used for the types which can easily be figured out, the remainder must belong to the 2nd type which is also then easily identified.

So by checking for a "T" at rs11544315 (DRA*010102) and an "A" at rs3135391 (DRA*010203), and either finding those or ruling them out, there are only three options left.

__Step 1__: determine if one or both types are as follows, with the allele unique to that set underlined and bolded (order is rs7192 rs8084 rs11544315 rs3135391):

GA

__T__G = DRA*010102

TAC

__A__ = DRA*010203

So if someone has "GG AA TT GG" then they are homozygous for DRA*010102, for example. Or if they have "GT AA CT AC" then they are heterozygous for both DRA*010102 and DRA*010203.

But in the event that they are only heterozygous for one of the above, such as with "GT AC CC AG", we can see that the "A" in the last pair means that they are heterozygous for DRA*010203 and can then subtract the known type from the alleles to see what remains. So if we subtract the DRA*010203 alleles of TACA from "GT AC CC AG" we're left with GCCG, which can be used to determine the DLA-DRA type.

Alternatively, neither DRA*010102 nor DRA*010203 are present, and the remaining options are two of the following three possibilities. Because the other two options have been found or ruled out, we now have some additional unique alleles in Step 2 which are underlined and bolded.

__Step 2__:

__G__CCG = DRA*010101

TCCG = DRA*010201

T

__A__CG = DRA*010202

If one of the types was already determined in Step 1, we subtract the known alleles to see what the remaining type is. In the "GT AC CC AG" example, we found DRA*010203 and were left with GCCG. Hence the 2nd type for that person must be DRA *010101.

But if neither type has been determined yet, we look for the now unique alleles in the remaining options. If rs7192 has one or two "G" alleles at this point, we know the person is respectively heterozygous or homozygous for DRA*010101. And if they have one or two "A" alleles at rs8084, we know they are heterozygous or homozygous for DRA*010202. But this only applies if Step 1 was completed first!

__Step 3__: Now that DRA*010101, DRA*010102, DRA*010202, and DRA*010203 have been definitely included or excluded for the patient, anything that is left should be TCCG, indicating DRA*010201. If trying to find this result prior to excluding everything else, all you get is a big mess and a bunch of guesswork. But by ruling out the other options first, in the proper order, it's possible to determine both HLA-DRA types with certainty.