They are the most common form of known polymorphism, people differ at approximately 1 in 1200 base pairs. Genetic variations Each individual has two identical copies of many genes, but some genes inherited from the mother will be different from their counterpart inherited from the father. A difference in one or more letters of a DNA sequence, referred to as a genetic variation, can modify the way a gene functions.
Genetic variations lead to a spectrum of observable differences, such as eye and hair color.
Genetic variations are also a major component of nearly all diseases, including cancer, diabetes and cardiovascular disease. Many chronic diseases are affected by multiple genetic variations. SNPs, are the most common type of genetic variation. SNPs are a change in a single letter of DNA text, such as replacing a G with a T in one location and on the complementary DNA strand replacing a C with an A. Another common variation is the insertion or deletion of one or several letters. A third common variation is an increase or decrease in the length of simple repeating DNA sequences.