Выпуск 1029. Подмененная дочь?

Unbeknownst to her grandmother, her granddaughter took her biomaterial for a DNA test with her mother. The result shocked everyone, it turned out to be zero. Substitution in the maternity hospital or adoption — what did the grandmother hide from her family for 44 long years? Or is the result of the examination conducted by the granddaughter erroneous?