A 9:3:3:1 Phenotypic Ratio in Genetics
A 9:3:3:1 phenotypic ratio is characteristic of the
A. F1 generation of a monohybrid cross.
B. F2 generation of a monohybrid cross.
C. F1 generation of a dihybrid cross.
D. F2 generation of a dihybrid cross.
E. F2 generation of a trihybrid cross.
Final answer:
The 9:3:3:1 phenotypic ratio is characteristic of the F2 generation of a dihybrid cross, where independent assortment and dominance produce this outcome for two different traits, each with two alleles following Mendelian inheritance patterns.
Explanation:
The correct answer to the question "A 9:3:3:1 phenotypic ratio is characteristic of the" is D. F2 generation of a dihybrid cross. This ratio results from a cross involving two genes, where each gene has two alleles and follows Mendelian inheritance patterns of dominance and segregation. The 9:3:3:1 ratio exemplifies the probability of obtaining the four different phenotypes when crossing two double heterozygotes (AaBb x AaBb). For instance, the ratio explains that in the F2 generation, there is a 9/16 chance for offspring to have both dominant phenotypes, a 3/16 chance for one dominant and one recessive phenotype (and vice versa), and a 1/16 chance for both recessive phenotypes.
The product rule can be applied to calculate these proportions; it dictates that the likelihood of two independent events both occurring is the product of their individual probabilities. Therefore, in the context of Mendelian dihybrid crosses, this product rule helps to determine the expected phenotypic ratios.