Law of dominance

Definition

The law of dominance states that in a pair of alleles, one is dominant and masks the effect of the other, which is recessive. This principle explains why heterozygous organisms display only the dominant trait in their phenotype.

5 Must Know Facts For Your Next Test

1. Gregor Mendel formulated the law of dominance based on his experiments with pea plants.
2. A dominant allele is represented by an uppercase letter, while a recessive allele is denoted by a lowercase letter.
3. In a heterozygous genotype (e.g., Aa), the trait associated with the dominant allele (A) will be expressed in the organism's appearance.
4. The law of dominance applies to traits controlled by a single gene with two alleles, but not all traits follow this simple pattern.
5. Mendel's observation of dominant and recessive traits laid the groundwork for modern genetics.

Review Questions

• Who formulated the law of dominance?
• How are dominant and recessive alleles represented symbolically?
• What happens to the phenotype in a heterozygous genotype according to the law of dominance?

Related terms

Genotype: The genetic makeup of an organism, consisting of both alleles inherited from its parents.

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

Allele: One of two or more versions of a gene that are found at the same place on a chromosome and can determine distinct traits.