Recombination Variance
Inheritance is not a clean fractional split. Recombination passes chromosomes down in uneven chunks, so the DNA inherited from a particular grandparent can differ sharply from the expected 25% and may eventually vanish from a descendant’s genome.
One grandparent may supply roughly 15% of your DNA while another supplies 30–35%—even though each occupies exactly one quarter of your grandparent family tree.
E1A family fraction is not a genetic allotment
The familiar 25% is an average, not a guaranteed delivery. During Genetic Recombination, chromosomes inherited from two parents are chopped and reassembled before being passed on. The resulting chromosome can therefore be heavily weighted toward one of your mother’s parents—for example, 70% from her father and 30% from her mother. Your mother then passes only part of her own recombined genome to you, turning that initial imbalance into unequal grandparent contributions. Each generation repeats the sampling, so genealogical ancestry and surviving DNA become increasingly different maps.
E1Unequal does not mean unconstrained
Recombination permits substantial variation around the expected share; it does not establish that every percentage is possible in every relationship. The supplied example demonstrates uneven grandparent contributions, but it does not provide enough evidence to infer a precise range or predict which grandparent’s DNA will be favored.
E1Separate the pedigree from the genome
When reading an ancestry result, compare its percentage with the family-tree expectation as a probabilistic benchmark, not a fixed quota. Treat a surprising grandparent share as a possible consequence of uneven recombination before concluding that the documented relationship must be wrong.
E1Episodes that teach this
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Revealing The Surprising DNA Facts! - FutureIQ
· explained at 10:59
15,171 views
You could end up with a situation where that one chromosome you got from your mom has 70% of the genes from the grandfather and only 30 from grandmother... so you can have just 15% from someone, 30-35% from someone else.