Final answer:
The Punnett square is a method for visualizing the possible genotypic and phenotypic outcomes of genetic crosses, conceived by Reginald C. Punnett. It is used to predict the results of monohybrid crosses, applying the principles of probability to determine ratios of genotypes and phenotypes among offspring.
Step-by-step explanation:
The method in question, which involves visualizing the genotypes and phenotypes resulting from the combination of gametes and displays all possible random fertilization events, is known as the Punnett square. Devised by Reginald C. Punnett, a British geneticist, a Punnett square is a visual representation used in genetics to predict the possible outcomes of a genetic cross or mating and their expected frequencies. It applies the rules of probability to illustrate genotypic and phenotypic ratios that result from a monohybrid cross.
For instance, in the case of true-breeding pea plants with yellow versus green pea seeds, where yellow seed color (YY) is dominant over green (yy), the Punnett square allows us to determine all possible genotypic combinations for their offspring. It shows that when crossing these two plants, all F₁ offspring will have the genotype Yy, resulting in yellow seeds, due to the dominance of the yellow allele.
When a self-cross of one of the Yy heterozygous offspring is performed, a 2 × 2 Punnett square reveals four possible combinations of alleles: YY, Yy, Yy, and yy. This results in a genotypic ratio of 1:2:1 and a phenotypic ratio of 3 yellow to 1 green, as the yellow phenotypes (YY and Yy) mask the green phenotype (yy).