When learning about genetics, you’ll often come across the terms genes and alleles. Though they are related, they serve different roles in determining your traits. Knowing the difference between genes and alleles helps clarify how we inherit certain characteristics and how genetic variations make each person unique.

What is a Gene?

A gene is a segment of DNA that contains the instructions for making a particular protein, which plays a crucial role in your body’s structure and function. Genes act as the blueprint for various traits, such as eye color, height, and skin tone. They are found on chromosomes, which are located in the nucleus of each cell.

For example, there is a specific gene that determines your eye color. This gene contains the information needed to create the pigment that gives your eyes their unique shade.

What is an Allele?

An allele is a different version of a gene. While genes determine traits, alleles create the variations in how these traits appear. Each gene has multiple alleles, and you inherit one allele from each parent. The combination of alleles you receive determines how a particular trait will be expressed.

For instance, the gene that controls eye color has multiple alleles, which is why people can have blue, green, brown, or hazel eyes. Alleles can be either dominant or recessive. A dominant allele will express its trait even if there’s only one copy present, while a recessive allele only shows its effect if both copies are recessive.

Key Differences Between Genes and Alleles

To put it simply, a gene provides the instructions for a trait, while alleles are the different versions of those instructions. Think of a gene as a recipe, and alleles as the variations of that recipe. The gene for eye color gives the general instructions for eye color, but the alleles determine whether your eyes will be brown, blue, or another color.

In plants, for example, the gene for flower color may have an allele for purple flowers and another for white flowers. The specific alleles present will dictate the actual color of the flower.

How Genes and Alleles Influence Traits

Genes and alleles work together to determine your traits. A single gene might control a specific characteristic, but alleles add variety by providing different versions of the trait. In some cases, a trait may be influenced by multiple genes interacting together.

Mendel’s famous pea plant experiments highlighted the difference between genes and alleles. The plants had a gene that controlled flower color, with two alleles—one for purple flowers and one for white flowers. Depending on the combination of alleles, the offspring would display either purple or white flowers.

The Role of Genes and Alleles in Genetic Testing

Genetic testing examines specific genes and their alleles to identify potential health risks. Variations in certain alleles can indicate whether a person is more likely to develop a particular condition. For example, in the case of cystic fibrosis, a genetic test looks for mutations in the CFTR gene. If a person has mutations in both alleles of this gene, they are likely to develop the disease.

Genetic testing is also used in pharmacogenomics, the study of how genes and alleles affect a person’s response to medications. By analyzing your alleles, doctors can tailor treatments to your unique genetic makeup, leading to more effective therapies.