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Null Allele

Null Alleles are a rare exception found in results from yDNA STR testing. Often appears as 0* in FTDNA STR reports. Basically a condition where the test cannot measure the STR due to an SNP change in the primer OR, more rarely, where a complete segment of DNA has been removed. In either case, a value cannot be determined using the traditional CE technique for STRs from FTDNA and others.

Null Alleles need to be specially handled in genetic distance calculations. But, unfortunately, often are not. Worse case, they should be ignored or treated as a universal match. Treating them as a mathematical zero in the same sense as any other measured value is a mistake. But unfortunately how they are dealt with in the FTDNA genetic distance calculation for determining STR matches. Often a Null Allele STR value can be accurately determined through another test technique not using the normal primer ((NGS for example).

STRs in palindromic regions of the yDNA are often susceptible to changes in this manner.

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