Which of the following scenarios best demonstrates the principle of independent assortment during meiosis?

• A. Linked genes on the same chromosome are always inherited together.
• B. Incomplete dominance results in a blending of parental phenotypes in the offspring.
• C. A monohybrid cross results in a 3:1 phenotypic ratio in the F2 generation.
• D. A dihybrid cross between two heterozygotes produces offspring with a 9:3:3:1 phenotypic ratio.

Answer: (D)

Verified step by step guidance

1. Step 1: Understand the principle of independent assortment, which states that alleles of different genes assort independently of one another during gamete formation in meiosis, leading to genetic variation.
2. Step 2: Analyze each scenario to see if it reflects independent assortment: linked genes do not assort independently because they are on the same chromosome and tend to be inherited together.
3. Step 3: Recognize that incomplete dominance involves blending of traits and does not relate to the independent segregation of different gene pairs.
4. Step 4: Note that a monohybrid cross showing a 3:1 phenotypic ratio involves only one gene and thus does not demonstrate independent assortment between different genes.
5. Step 5: Identify that a dihybrid cross between two heterozygotes producing a 9:3:3:1 phenotypic ratio is the classic example demonstrating independent assortment, as it shows how two gene pairs segregate independently to produce four phenotypic classes.