Understanding Alleles: Definition, Examples, and Case Studies

Discover the world of alleles and how they impact traits and diseases. Learn about dominant and recessive alleles through real-life examples and case studies.

What are Alleles?

Alleles are alternative forms of a gene that can be found at the same location on a chromosome. Each individual inherits two alleles for each gene, one from their mother and one from their father.

Types of Alleles

  • Dominant alleles: These alleles are expressed when present, masking the effects of recessive alleles.
  • Recessive alleles: These alleles are only expressed when no dominant allele is present.

Examples of Alleles

One common example of alleles is for the gene that determines blood type. The ABO blood group system is controlled by three alleles: A, B, and O. A person can have blood type A, B, AB, or O depending on the combination of alleles inherited from their parents.

Case Studies

Studies have shown how alleles can impact various traits and diseases. For example, the BRCA1 and BRCA2 genes have specific alleles that are associated with an increased risk of developing breast and ovarian cancer. Understanding these alleles can help individuals make informed decisions about their health.

Statistics on Alleles

According to genetic studies, humans share about 99.9% of their DNA sequence, but it is the variation in alleles that accounts for the differences in traits among individuals. Alleles play a crucial role in genetic diversity and evolution.

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