What is a Single nucleotide polymorphisms SNP?
The 46 human chromosomes come in pairs, one in each pair is inherited from each parent. Although each chromosome of a pair contains the same genes in the same order, the sequences are not identical. On average, one in every 500 to 1000 base pairs of our genome differs from the one found in the majority of people. These randomly occurring changes are passed from generation to generation and account for a high proportion of the DNA differences between us. It is estimated that up to ten million such variations lie hidden in our genome. When such a variation is present in at least one percent of a particular population, for example an ethnic group, it is referred to as a single nucleotide polymorphism, or SNP (pronounced “snip”). For example, one individual may have a cytosine (C) at a specific point in his DNA, whereas another individual may have a thymine (T). If the individuals possess two copies of T or of C at this location, one on each chromosome pair, they are referred to as “homozy
