Allele

Definition

An allele is a variant form of a gene that arises by mutation and is found at the same place on a chromosome as another allele. Alleles can be dominant or recessive, influencing how traits are expressed in an organism, and they play a crucial role in genetic variation and inheritance patterns.

5 Must Know Facts For Your Next Test

1. Alleles are responsible for the genetic diversity seen within a population, contributing to variations in traits such as color, size, and shape.
2. An organism can be homozygous for a trait if it has two identical alleles or heterozygous if it has one dominant and one recessive allele.
3. The concept of multiple alleles exists when there are more than two possible forms of a gene within a population, leading to various phenotypes.
4. Alleles are inherited from an organism's parents, with one allele coming from each parent, contributing to the genetic makeup of the offspring.
5. Different combinations of alleles can lead to dominant or recessive expressions of traits, influencing how those traits are passed on through generations.

Review Questions

• How do alleles contribute to genetic variation within a population?
  • Alleles contribute to genetic variation by introducing different forms of genes that can express varying traits among individuals. When alleles recombine during reproduction, they create new combinations that enhance diversity within the gene pool. This variation is essential for natural selection and adaptation as it allows populations to better respond to environmental changes.
• Compare and contrast dominant and recessive alleles in terms of their effects on phenotype.
  • Dominant alleles mask the expression of recessive alleles in heterozygous conditions, meaning that only one copy of a dominant allele is needed for the associated trait to be expressed in the phenotype. In contrast, recessive alleles require two copies (one from each parent) to manifest in the phenotype. This difference affects how traits are inherited and observed in offspring, leading to diverse phenotypic outcomes.
• Evaluate the impact of allelic variation on evolution and natural selection processes.
  • Allelic variation plays a crucial role in evolution as it provides the raw material for natural selection. When individuals with beneficial alleles have a higher reproductive success, these advantageous traits become more common in the population over generations. This process drives evolutionary change and adaptation, demonstrating how alleles are foundational to understanding evolutionary dynamics and species survival.

Related terms

genotype: The genetic constitution of an individual, representing the specific alleles they possess for a given trait.

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

homozygous: A condition where an individual has two identical alleles for a specific gene, either dominant or recessive.