Calculate how likely your baby is to inherit rare genetic traits including red hair, grey eyes, heterochromia, natural albinism, and left-handedness. Based on population frequency data.
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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.
Natural red hair is one of the rarest hair colour combinations in the world, occurring in only 1–2% of the global population. Both parents must carry at least one copy of the MC1R gene variant — and even then, there is only a 25% chance of a red-haired child.
Rare physical features result from low-frequency recessive alleles in the population pool. Many recessive mutations arose historically as adaptations in specific climates (e.g. fair skin/red hair in high-latitude environments). For these traits to express, both parents must contribute the rare recessive gene.
Low occurrence rates in the population pool. Many are recessive traits that require two matching carrier alleles to express.
Traits like ocular albinism, green eyes, heterochromia, and situs inversus are among the rarest structural phenotypes in humans.
Carriers can pass the allele through generations without expression, until a carrier partners with another carrier, bringing the trait back.
Allele distribution is heavily linked to historical demographics. Red hair is rare globally but occurs in up to 13% of Scotland's population.
Yes. If both parents are healthy carriers of a recessive mutation (like albinism or red hair), they have a 25% probability of having an expressing child.
Among physical appearance traits, heterochromia (different colored eyes) and natural albinism are exceptionally rare, affecting less than 0.1% of people.
Yes, it is polygenic with approximately 25% heritability. While it has genetic roots, environmental factors in the womb also play a role.
Only if there is a strong selective advantage or genetic drift within a closed population that increases the frequency of the recessive allele over generations.