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Understanding Genes and Alleles: What’s the Difference?

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When exploring genetics, the terms genes and all of them often cause confusion. Though closely related, they represent different aspects of our genetic makeup. This article will explain these concepts and highlight the key differences between genes and alleles.
What Is a Gene?
A gene is a segment of DNA that carries instructions for producing proteins, which are essential for the body's structure and functions. These proteins help shape everything from your physical traits, like eye color, to how your body processes food. Genes are located on chromosomes within the nucleus of your cells, each occupying a specific spot known as a locus.
For example, the gene responsible for eye color contains instructions for making pigments that determine eye color. Genes can control various characteristics, such as:
  • Physical traits like height and hair color
  • Metabolic processes and functions within the body
What Is an Allele?
An allele is a variation of a gene. Since genes come in pairs—one inherited from each parent—each individual has two alleles for every gene. These alleles can be identical or different, contributing to genetic diversity. For instance, the gene for eye color has different alleles, which is why people can have blue, brown, green, or hazel eyes.
There are two main types of alleles:
  • Dominant Alleles : These express their trait if at least one copy is present.
  • Recessive Alleles : These only express their trait if both copies are recessive.
For example, if blue eyes are caused by a dominant allele, having one dominant allele is enough for the person to have blue eyes.
Difference Between Genes and Alleles
The difference between genes and alleles can be compared to the difference between a general concept and its specific versions. A gene is a section of DNA that controls a particular trait, while an allele is a variant form of that gene. In other words, while a gene determines a trait, they determine the variations of that trait. 
For instance, consider a gene that determines flower color. This gene can have different alleles that result in purple or white flowers. The gene itself controls the trait of flower color, but the specific alleles present determine whether the flower will be purple or white.
Genes, Alleles, and Genetic Testing
Understanding the relationship between genes and alleles is crucial for genetic testing. These tests allow scientists to analyze DNA and identify variations that may affect health, disease risk, or drug responses.
Detecting Mutations
Genetic tests can identify mutations in alleles that may lead to diseases. For instance, in cystic fibrosis, testing looks for mutations in the CFTR gene. If both of them are mutated, the individual will develop the condition.
Carrier Status
Genetic testing can reveal whether an individual carries a recessive allele for a condition, which they might pass on to their children. For example, someone who carries the allele for sickle cell anemia may not have the disease but can still pass the allele to their offspring.
Assessing Disease Risk
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