What Are Genes?
A Gene is a section of our DNA that act as instructions to create the proteins bodies need to function properly.
- Human DNA consists of nearly 3 billion nucleotides
- Humans have approximately 20,000 to 25,000 genes
- Every person has two copies of each gene – one from their mother and one from their father
- Our DNA is 99.5% identical to one another
How Our Genes Can Differ
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.
Why Are SNPs Important?
A SNP can impact a cell’s ability to produce the proteins our bodies require to function normally. Abnormal function can:
- Impact how a person processes specific drugs/medications
- Impact the adverse drug events (ADEs) or side effects from specific drugs/medications?
- Be the cause of certain diseases or conditions
Genotypes, Phenotypes & Star Alleles
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.
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