Genetic Crosses and Chance
Pick a type of cross and the genotype of each parent, and see the exact Punnett square, the expected ratio and a random family of offspring drawn from it. Compare the counts with the ratio using a chi-squared test, and see how far chance moves a small family compared with a large one.
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What you can adjust
- Type of cross
- 0 – 4
- First parent's genotype
- 0 – 8
- Second parent's genotype
- 0 – 8
- Number of offspring
- 4 – 1000
- Random seed
- 1 – 99
How the alleles of the gene (or genes) work together. The genotype lists below change to match.
The alleles this parent carries (its genotype), and the trait it shows (its phenotype). Each gamete gets one allele of each gene, at random. In the fruit-fly cross this is the mother.
The alleles the other parent carries. In the fruit-fly cross this is the father, who has one X and a Y.
How many offspring the random family has. Each offspring's chance is the same and does not depend on the others, but small families often stray far from the expected ratio.
Fixes the random draw: the same seed and settings always give the same family. Change it to see how chance alone changes the counts.