Major vs. Reference Allele: A Simple Explanation

Imagine DNA as a blueprint that makes each person unique. Scientists have combined the DNA from many anonymous volunteers to create a standard blueprint, called the reference genome.

Think of a specific spot on this blueprint like a puzzle piece. The puzzle piece can be one of two types: the reference allele or the alternative allele. The reference allele is the base found at a specific spot in the reference genome. If the puzzle piece is different from the reference allele, we call it the alternative allele.

Here's where it gets interesting: some puzzle pieces appear more frequently than others. When a puzzle piece (allele) is common, we call it the major allele, and when it's rarer, we call it the minor allele.

What's cool is that either the reference allele or the alternative allele can be major—it depends on which one shows up more in the blueprint. So, sometimes the regular puzzle piece (reference allele) is major, and other times the different one (alternative allele) takes the major spotlight.