What's makes you unique?

Human Genetics Variation

The genetic differences in and among populations are referred to as human genetic variation. Polymorphism refers to the fact that any given gene might have numerous variants (alleles) in the human population.

Genetically, no two people are alike. Due to mutations that occur during development and gene copy-number variation, even monozygotic twins (who grow from the same zygote) have occasional genetic differences. Techniques like genetic fingerprinting rely on differences between people, even those who are closely related. There are 324 million identified variations from sequenced human genomes as of 2017. The average variation between an individual's genome and the reference genome was 20 million base pairs in 2015.

There are at least three reasons why populations have genetic variety. If an allele confers a competitive advantage, natural selection may offer an adaptive advantage to individuals in a certain environment. Alleles that are under selection are likely to appear exclusively in areas where they provide an advantage. Genetic drift, which is the result of random changes in the gene pool under settings where most mutations are neutral, is a second significant process (that is, they do not appear to have any positive or negative selective effect on the organism).

Finally, small migrant populations have statistical differences – known as the founder effect – from the overall populations where they originated; when these migrants settle new areas, their descendant population typically differs from their population of origin, with different genes predominating and less genetic diversity.