Allele

Definition

An allele is a variant form of a gene that can exist at a specific location on a chromosome. Alleles can be dominant or recessive, influencing the expression of traits in an organism. The combination of alleles inherited from parents determines an individual's genotype, which in turn affects their phenotype, or observable characteristics.

5 Must Know Facts For Your Next Test

1. An organism inherits one allele from each parent, resulting in a pair of alleles that determine specific traits.
2. Dominant alleles mask the effect of recessive alleles in heterozygous individuals, meaning the dominant trait is expressed in the phenotype.
3. Mutations can lead to the formation of new alleles, contributing to genetic variation within a population.
4. Different populations may have distinct allele frequencies, affecting how traits are expressed and leading to diversity among organisms.
5. Alleles can be associated with certain inherited disorders when a specific allele is linked to the manifestation of a disease-causing trait.

Review Questions

• How do dominant and recessive alleles interact to determine an organism's phenotype?
  • Dominant alleles express their traits even when only one copy is present in a heterozygous organism, while recessive alleles only manifest their traits when two copies are present. For example, if a dominant allele for tall stature is paired with a recessive allele for short stature, the organism will display the tall phenotype. This interaction highlights how different alleles work together to shape physical traits.
• Discuss the role of alleles in the inheritance patterns observed in Mendelian genetics.
  • In Mendelian genetics, alleles are crucial for understanding how traits are passed from parents to offspring. Each parent contributes one allele for each gene, leading to various combinations that determine the genotype of the offspring. The classic experiments with pea plants by Gregor Mendel illustrated patterns such as segregation and independent assortment, showcasing how alleles influence trait inheritance across generations.
• Evaluate the implications of genetic mutations on allele diversity within populations and their connection to inherited disorders.
  • Genetic mutations can create new alleles, increasing genetic diversity within populations. This diversity is essential for natural selection and adaptation to changing environments. However, certain mutations may also lead to harmful alleles associated with inherited disorders. Understanding these connections helps in identifying genetic risks and developing strategies for managing genetic diseases within populations.

Related terms

Genotype: The genetic makeup of an organism, represented by the combination of alleles for a specific gene.

Phenotype: The physical expression or characteristics of a trait determined by the genotype and environmental factors.

Homozygous: A genetic condition where an individual has two identical alleles for a particular gene.