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Punnett squares for each combination of parents' colour vision status giving probabilities of their offsprings' status, each cell having 25% probability in theory. The Punnett square is a square diagram that is used to predict the genotypes of a particular cross or breeding experiment.
The first uses of test crosses were in Gregor Mendel’s experiments in plant hybridization.While studying the inheritance of dominant and recessive traits in pea plants, he explains that the “signification” (now termed zygosity) of an individual for a dominant trait is determined by the expression patterns of the following generation.
Here the relation between genotype and phenotype is illustrated, using a Punnett square, for the character of petal color in pea plants. The letters B and b represent genes for color, and the pictures show the resultant phenotypes. This shows how multiple genotypes (BB and Bb) may yield the same phenotype (purple petals).
Dihybrid crosses are easily visualized using a 4 x 4 Punnett square. In these squares, the dominant traits are uppercase, and the recessive traits of the same characteristic is lowercase. In the following case the example of pea plant seed is chosen. The two characteristics being compared are; Shape: round or wrinkled (Round (R) is dominant)
A Punnett square for one of Mendel's pea plant experiments - self-fertilization of the F1 generation, shows that inheritance is particulate, not blending. Further information: Mendelian inheritance and Germ plasm
Punnett is probably best remembered today as the creator of the Punnett square, a tool still used by biologists to predict the probability of possible genotypes of offspring. His Mendelism (1905) is sometimes said to have been the first textbook on genetics; it was probably the first popular science book to introduce genetics to the public.
This is a Punnett square for Rh factor inheritance. This square specifically shows two heterozygous Rh positive parents and the possible genotypes/phenotypes the offspring could have. The D antigen is inherited as one gene (on the short arm of the first chromosome, p36.13–p34.3) with various alleles. Typically, Rhesus positive people have an ...
Punnett square for three-allele case (left) and four-allele case (right). White areas are homozygotes. Colored areas are heterozygotes. Consider an extra allele frequency, r. The two-allele case is the binomial expansion of (p + q) 2, and thus the three-allele case is the trinomial expansion of (p + q + r) 2.