An allele is a different version of the same gene, like an alternative “spelling” of the DNA at one specific spot on a chromosome. Each person typically has two alleles for most genes, one inherited from each parent, and together these help determine traits such as eye color, blood type, or height.

Core idea

  • A gene is a stretch of DNA that influences a particular trait (for example, eye color).
  • An allele is one specific variant of that gene at a particular locus (location) on the DNA.
  • People usually carry two alleles for each gene; if both copies are the same, they are homozygous, and if they are different, they are heterozygous.

Simple example

  • Think of a “flower color” gene that can come in a red version and a white version.
  • “Red” and “white” here are two alleles of the same gene, not two different genes.
  • The combination of alleles an organism has (its genotype) produces what you see (its phenotype), such as a red or pink flower.

Dominant and recessive

  • Some alleles are dominant , meaning their effect shows even if only one copy is present, while others are recessive , showing only when both copies are that recessive version.
  • For example, a dominant allele for a trait (like tallness in a classic pea-plant example) can mask a recessive allele for shortness when both are present together.

Why alleles matter today

  • Allelic differences explain why people in 2026 genetic studies can respond differently to the same drug, have different disease risks, or show different physical traits even within the same family.
  • Population genetics tracks how alleles become more or less common over time through mutation, selection, and drift, which is crucial for fields like medical genetics and evolutionary biology.

Information gathered from public forums or data available on the internet and portrayed here.