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Fantasy Bloodline & Trait Calculator

Calculatrice gratuite de génétique fantastique pour OC.

Quand l’utiliser

Use when designing a character's family tree or a fan-fiction OC's offspring odds. Standard Mendelian inheritance — perfect for a simple visible trait.

Comparaison

A bare Punnett square calculator does the same math. This one wraps it in narrative trait names that suit world-builders.

Enter your values below. Calculations run locally as you type.

Comment ça marche

Two parents combine into a Punnett square: each cell is one of four equally likely offspring genotypes (AA, Aa, aA, aa).

Aa and aA are functionally identical — both heterozygous. AA shows the trait; aa hides it; Aa shows it but carries the recessive.

Percentages are simply the count of matching outcomes divided by four.

FAQ

Does it support multiple traits?

Not yet — one trait at a time. Run the tool again with the next trait.

How does dominance work?

Standard Mendelian: A is dominant over a. Aa shows the trait; aa does not.

What do the Punnett square odds represent?

They show the probability that offspring inherit each genotype based on the alleles each parent can pass on. For example, two heterozygous parents yield a classic 1:2:1 genotype ratio and a 3:1 dominant-to-recessive appearance ratio.

What is the difference between homozygous and heterozygous?

Homozygous means both copies of the gene are the same allele (either both dominant or both recessive), while heterozygous means one of each. A heterozygous parent can pass on either allele, which is why it produces variable offspring.

Exemple concret

Entrée

Trait "Silver Hair", Parent A: Aa (carrier), Parent B: Aa (carrier).

Sortie

75% chance child shows trait. 25% no trait.

AA × AA = 25% homozygous dominant, 50% heterozygous (carriers, show trait), 25% homozygous recessive (no trait).

Pièges courants

  • Real genetics involves multiple genes and incomplete dominance.
  • Sex-linked traits (X chromosome) need a different model.
  • Magic systems often break inheritance rules entirely — use as a baseline.

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