Incomplete Dominance

Definition

Incomplete dominance is a genetic phenomenon where neither allele is completely dominant over the other, resulting in a third phenotype that is a blending of the two parental traits. This occurs when heterozygous individuals display a phenotype that is intermediate between the phenotypes of the two homozygous parents, illustrating how genetic expression can be more complex than simple dominance.

5 Must Know Facts For Your Next Test

1. In incomplete dominance, the offspring's phenotype is a mix of both parental traits, like red and white flowers producing pink flowers.
2. This type of inheritance demonstrates that some traits can be influenced by multiple alleles, leading to various phenotypic expressions.
3. Incomplete dominance is different from codominance, where both traits are fully expressed rather than blended.
4. This genetic principle can be observed in various organisms, including plants and animals, illustrating its broad relevance in genetics.
5. In human genetics, incomplete dominance can be seen in certain conditions like hypercholesterolemia, where heterozygous individuals exhibit an intermediate level of cholesterol.

Review Questions

• How does incomplete dominance differ from complete dominance in genetic inheritance?
  • Incomplete dominance differs from complete dominance in that it results in a blending of traits rather than one allele completely masking the other. In complete dominance, the dominant allele's trait fully expresses itself in the phenotype of heterozygous individuals, while in incomplete dominance, the phenotype is an intermediate expression. This shows how genetic interactions can lead to diverse appearances among offspring.
• Evaluate the implications of incomplete dominance for understanding genetic variation within populations.
  • Incomplete dominance has significant implications for understanding genetic variation as it showcases how traits can combine in different ways rather than being strictly governed by dominant and recessive alleles. This blending allows for a wider range of phenotypes within populations, contributing to biodiversity. It also emphasizes the importance of considering multiple alleles and gene interactions when studying genetics.
• Synthesize information about incomplete dominance and its relevance to both plant and animal breeding practices.
  • Incomplete dominance plays a crucial role in breeding practices by allowing breeders to achieve desired traits through controlled crosses. For example, when breeding plants or animals with different colors or qualities, incomplete dominance can lead to unique intermediate phenotypes that may enhance aesthetics or productivity. Understanding this principle enables breeders to predict outcomes more accurately and select for traits that blend well together, ultimately impacting agricultural and horticultural advancements.

Related terms

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

Phenotype: The observable physical or biochemical characteristics of an organism, determined by both genetic makeup and environmental influences.

Codominance: A genetic situation where both alleles in a heterozygote are fully expressed, resulting in offspring with a phenotype that shows both traits distinctly.