Genetic study finds grandparents contribute equally to grandchildren's DNA

Genetic analysis shows that each grandparent—paternal grandfather, paternal grandmother, maternal grandfather, and maternal grandmother—contributes roughly 25% of a grandchild's DNA. While mitochondrial DNA is passed only from the mother and the Y chromosome only from the father, both represent a very small portion of the total genetic material and do not affect emotional bonds.

Psychologist John Bowlby's attachment theory explains that a child's sense of closeness to caregivers is shaped by early emotional experiences, not by the proportion of DNA inherited from each grandparent.