Question

question 48
1.5 pts
two plants are crossed, resulting in offspring with a 3:1 ratio for a particular trait. what does this suggest about the trait?
that the parents were true - breeding for contrasting traits
that the trait shows incomplete dominance
that a blending of traits has occurred
that the parents were both heterozygous for a single trait

Explanation:

1. Analyze each option:

• Option 1: True - breeding parents (homozygous) for contrasting traits would produce offspring with a 1:0 ratio (all heterozygous with dominant trait) in the F1 generation, not 3:1. So this is incorrect.
• Option 2: Incomplete dominance results in a 1:2:1 ratio (e.g., red, pink, white in flower color), not 3:1. So this is incorrect.
• Option 3: Blending inheritance is an outdated concept, and a 3:1 ratio is based on Mendelian genetics (particulate inheritance), not blending. So this is incorrect.
• Option 4: When two heterozygous parents (Aa × Aa) for a single trait are crossed, using a Punnett square, the genotypic ratio is 1 AA: 2 Aa: 1 aa, and the phenotypic ratio is 3 (dominant - AA, Aa, Aa):1 (recessive - aa), which matches the 3:1 ratio given. So this is correct.

Answer:

D. that the parents were both heterozygous for a single trait