Dominant allele

Definition

A dominant allele is a variant of a gene that masks the effect of a recessive allele when both are present in a genotype. This means that if an individual has at least one dominant allele for a particular trait, that trait will be expressed in their phenotype, overshadowing any influence from the recessive allele. Understanding dominant alleles is essential for grasping inheritance patterns and how traits are passed from one generation to the next.

5 Must Know Facts For Your Next Test

1. Dominant alleles are represented by uppercase letters in genetic notation, while recessive alleles are represented by lowercase letters.
2. In a heterozygous individual, the presence of one dominant allele is sufficient for the dominant trait to be expressed.
3. The concept of dominant and recessive alleles was first systematically studied by Gregor Mendel through his experiments with pea plants.
4. Dominant alleles can lead to traits that are more visibly represented in populations, affecting the phenotypic ratios in offspring.
5. Certain traits determined by dominant alleles can become more common in a population if the allele confers some sort of advantage or is linked to reproductive success.

Review Questions

• How does the presence of a dominant allele affect the expression of traits in an organism?
  • The presence of a dominant allele significantly influences trait expression in an organism because it can mask the effects of a recessive allele. When an individual possesses at least one dominant allele for a specific trait, that trait will be expressed in their phenotype. For instance, in the case of flower color in pea plants, a plant with at least one dominant allele for purple flowers will have purple flowers, regardless of whether it has one or two recessive alleles for white flowers.
• What implications do dominant alleles have on genetic diversity within a population?
  • Dominant alleles can impact genetic diversity by influencing which traits become more common within a population. When traits associated with dominant alleles provide survival or reproductive advantages, these alleles can spread quickly through generations. This may lead to decreased genetic variability if certain dominant traits overshadow others, potentially limiting the overall adaptability of the population to changing environments.
• Evaluate how understanding dominant and recessive alleles contributes to advancements in fields like genetics and medicine.
  • Understanding dominant and recessive alleles is crucial for advancements in genetics and medicine as it lays the foundation for predicting inheritance patterns and identifying genetic disorders. By knowing which traits are controlled by dominant alleles, researchers can trace these traits through generations and assess their likelihood of appearing in offspring. This knowledge can also help in genetic counseling, where families can be informed about potential inherited conditions based on the presence of specific dominant or recessive alleles. Furthermore, it aids in developing targeted therapies and interventions for genetic diseases.

Related terms

recessive allele: A recessive allele is a variant of a gene that only expresses its trait in the phenotype when two copies are present, meaning it can be masked by a dominant allele.

homozygous: Homozygous refers to having two identical alleles for a particular gene, whether they are both dominant or both recessive.

heterozygous: Heterozygous describes having two different alleles for a particular gene, typically consisting of one dominant and one recessive allele.