Students taking a genetics exam were expected to answer the following question by converting data to a 'meaningful ratio' and then solving the problem. The instructor assumed that the final ratio would reflect two gene pairs, and most correct answers did. Here is the exam question: 'Flowers may be white, orange, or brown. When plants with white flowers are crossed with plants with brown flowers, all the F₁ flowers are white. For F₂ flowers, the following data were obtained: 48 white 12 orange 4 brown Convert the F₂ data to a meaningful ratio that allows you to explain the inheritance of color. Determine the number of genes involved and the genotypes that yield each phenotype.' Solve the problem for two gene pairs. What is the final F₂ ratio?

Key Concepts

Mendelian Inheritance

Mendelian inheritance refers to the principles of heredity established by Gregor Mendel, which describe how traits are passed from parents to offspring through dominant and recessive alleles. In this context, the inheritance of flower color can be explained by Mendel's laws, particularly the law of segregation and the law of independent assortment, which help predict the phenotypic ratios in offspring based on parental genotypes.

Phenotypic Ratio

A phenotypic ratio is the relative number of offspring manifesting a particular trait or combination of traits, expressed in simplest form. In the given problem, the F₂ generation's flower color data (48 white, 12 orange, 4 brown) can be converted into a ratio that reflects the inheritance pattern, which is essential for understanding how the traits are distributed among the offspring.

Dihybrid Cross

A dihybrid cross involves examining the inheritance of two different traits, each controlled by different gene pairs. In this scenario, the flower color is influenced by two gene pairs, leading to a phenotypic ratio of 9:3:3:1 in the F₂ generation when both traits assort independently. Understanding this concept is crucial for determining the genotypes that yield each phenotype and for calculating the final F₂ ratio.