What is an example of incomplete dominance? a. Polydactyly b. Snapdragon flower colors C. Blood groups d. Wrinkly and yellow peas e. None of these
The correct answer and explanation is:
Correct Answer: b. Snapdragon flower colors
Explanation:
Incomplete dominance is a type of inheritance in genetics where neither allele is completely dominant over the other. Instead of one trait completely masking the other, the resulting phenotype is a blend or intermediate of the two parent traits.
A classic and widely accepted example of incomplete dominance occurs in snapdragon flower colors. When a snapdragon plant with red flowers (RR) is crossed with one with white flowers (WW), the resulting offspring (RW) have pink flowers. The pink color is an intermediate expression of both red and white alleles. This blending shows that neither the red nor the white allele is completely dominant, which defines incomplete dominance.
Each of the other answer choices does not represent incomplete dominance:
- a. Polydactyly is a condition of having extra fingers or toes and is usually inherited as a dominant trait, not an example of incomplete dominance.
- c. Blood groups involve multiple alleles and codominance, particularly the ABO blood group system. In codominance, both alleles are expressed equally (e.g., in type AB blood, both A and B antigens are expressed). This is different from the blending seen in incomplete dominance.
- d. Wrinkly and yellow peas were observed in Mendel’s pea plant experiments. Wrinkled and smooth textures, as well as yellow and green colors, followed complete dominance, where one trait fully masks the other. This does not show an intermediate form.
- e. None of these is incorrect because there is a valid example provided.
Therefore, snapdragon flower colors are the best and most accurate example of incomplete dominance, where heterozygous individuals show a phenotype that is a mix of the two parental traits rather than resembling only one of them.