Enter all four grandparents' traits to calculate the probability of your baby inheriting features directly from grandma or grandpa. Useful for understanding multi-generational trait flow.
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Generated at traitgen.com, Free genetics education. Not medical advice.
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⚠️ Educational only. Probability estimates based on genetic models, not medical advice.
Traits can skip a generation because genes from grandparents are passed to parents who may be carriers — not expressers — and then re-emerge in grandchildren. This is especially common with blue eyes, freckles, and red hair.
A grandchild inherits exactly 25% of their DNA from each grandparent on average. However, because genes are passed down in chromosome blocks, the actual percentage of DNA shared with a specific grandparent can range between 18% and 32%. This variation explains why a baby might look exceptionally like one grandparent.
Grandparents pass 50% of their DNA to the parent, who then passes 50% of their DNA to the grandchild, creating a statistical 25% link.
Recessive grandparent alleles (e.g., for blue eyes or red hair) are passed to parents where they are masked, only to combine and show up in the grandchild.
If a grandparent has a recessive trait (aa) and the parent does not express it (Aa), the trait skips a generation and can appear in the child if both parents contribute the 'a' allele.
Highly heritage-linked traits like eye color, freckles, dimples, and earlobe structure show very predictable Mendelian inheritance patterns across three generations.
Yes, if the baby inherits a high concentration of dominant appearance genes from that grandparent's lineage, they can resemble them closely.
Statistically, it is random. However, due to X-chromosome inheritance, male babies get their X-chromosome exclusively from their mother, which traces back to maternal grandparents.
Neither. The dominance of a gene is determined by the allele structure (e.g. brown eyes dominate over blue), not which parent passes it down.
If both parents were carriers of grandpa's recessive eye color allele, the child had a 25% chance of inheriting it, allowing it to re-emerge.