Incomplete dominance

Definition

Incomplete dominance is a genetic situation in which one allele does not completely dominate another allele, resulting in a phenotype that is a blending of both traits. This phenomenon showcases how characteristics are inherited, allowing for a range of expressions rather than just dominant or recessive traits. It highlights the complexity of inheritance patterns and shows that traits can exhibit intermediate forms in offspring.

5 Must Know Facts For Your Next Test

1. In incomplete dominance, the heterozygous phenotype is a mix of the dominant and recessive traits, creating an intermediate appearance.
2. A classic example of incomplete dominance is seen in the flower color of snapdragons, where red and white flowers produce pink offspring.
3. This type of inheritance can complicate predictions in genetic crosses because offspring do not simply display dominant or recessive traits.
4. Incomplete dominance reveals that multiple alleles can influence a single trait, leading to diverse phenotypic outcomes.
5. It provides a clearer understanding of genetic variation within populations as it demonstrates how traits can blend rather than segregate.

Review Questions

• How does incomplete dominance differ from complete dominance in terms of phenotypic expression?
  • Incomplete dominance differs from complete dominance because, in incomplete dominance, the heterozygous phenotype is a blend of the two alleles rather than displaying just the dominant trait. For example, if one parent has a red flower (RR) and the other has a white flower (WW), the offspring will have pink flowers (RW), illustrating the blending of traits. In contrast, complete dominance would result in all offspring showing only the dominant phenotype.
• Discuss an example of incomplete dominance and explain how it illustrates the concept.
  • An example of incomplete dominance can be seen in snapdragon flowers where crossing red-flowered plants with white-flowered plants yields offspring with pink flowers. This illustrates that neither allele is completely dominant over the other; instead, they combine to create a new phenotype. The pink flowers represent an intermediate trait that results from the mixing of red and white pigments, emphasizing the idea that some genetic traits can express themselves as blends.
• Evaluate the significance of incomplete dominance in understanding genetic variation and inheritance patterns.
  • The significance of incomplete dominance lies in its ability to illustrate the complexity of inheritance patterns and genetic variation within populations. By showing that alleles can blend rather than follow simple dominant-recessive relationships, it challenges traditional Mendelian genetics and highlights the role of multiple alleles in shaping phenotypes. This understanding is crucial for fields like plant breeding and genetics research, where recognizing intermediate traits can lead to better predictions and applications in biodiversity conservation.

Related terms

codominance: A genetic scenario where both alleles in a heterozygote are fully expressed, resulting in offspring with distinct traits from both parents.

phenotype: The observable physical and physiological traits of an organism, which result from the interaction of its genotype with the environment.

alleles: Different versions of a gene that determine specific traits, where each organism inherits one allele from each parent.