Question

Four sisters begin attending your school. One has brown hair and brown eyes. Another has brown hair and blue eyes. The third also has blue eyes, but blond hair. The fourth has blond hair, too, but she has brown eyes. Explain how the principle of independent segregation accounts for these sisters having four different phenotypes for two traits.

Answer 1

According to the Law of Independent Assortment, (Inheritance Law), separate genes for separate traits are passed independently of one another from parents to offspring. So, the biological selection of a particular gene in the gene pair for one trait to be passed to the offspring has nothing to do with the selection of the gene for any other trait. More precisely the law states that alleles of different genes assort independently of one another during gamete formation. When mixing two traits, the ratio between dominant and recessive phenotypes will be 9:3:3:1.