A Gene is a section of our DNA that act as instructions to create the proteins bodies need to function properly.

Sometimes, for reasons that are not totally clear, one or both copies of a genes can be altered. Genetic variation of the same gene between people is called an Allele.

Often, an Allele by a nucleotide change at a specific location in the DNA strand, often within or near a gene. This change of base nucleotide is called a Single Nucleotide Polymorphism or SNP (pronounced “snip”) and is often identified by an assigned unique number.

The expected or base nucleotide (the one common to most people) at the specified location is called the wild type.

A SNP can impact a cell’s ability to produce the proteins our bodies require to function normally.   Abnormal function can:

We call a mutation or a group of mutations the Genotype. In the example above, the values (G;G G;A A;A) are the genotype for SNP rs6025. An individual will be able to say, “I have a G;G genotype for SNP rs6025” similar to how the say “My blood type is O-negative”.

The resulting physical trait or abnormality associated with a given genotype is called a Phenotype.

Sometimes, more than one mutation occurs for a given gene. These mutations are grouped according to their pattern and given a name called a Star Allele. The pair of star alleles (e.g. *2/*2) becomes the genotype for that specific gene.