<P> Human genetic variation is the genetic differences in and among populations . There may be multiple variants of any given gene in the human population (alleles), a situation called polymorphism . </P> <P> No two humans are genetically identical . Even monozygotic twins (who develop from one zygote) have infrequent genetic differences due to mutations occurring during development and gene copy - number variation . Differences between individuals, even closely related individuals, are the key to techniques such as genetic fingerprinting . As of 2017, there are a total of 324 million known variants from sequenced human genomes . As of 2015, the the typical difference between the genomes of two individuals was estimated at 20 million base pairs (or 0.6% of the total of 3.2 billion base pairs). </P> <P> Alleles occur at different frequencies in different human populations . Populations that are more geographically and ancestrally remote tend to differ more . The differences between populations represent a small proportion of overall human genetic variation . Populations also differ in the quantity of variation among their members . The greatest divergence between populations is found in sub-Saharan Africa, consistent with the recent African origin of non-African populations . Populations also vary in the proportion and locus of itrogressed genes they received by archaic admixture both inside and outside of Africa . </P> <P> The study of human genetic variation has evolutionary significance and medical applications . It can help scientists understand ancient human population migrations as well as how human groups are biologically related to one another . For medicine, study of human genetic variation may be important because some disease - causing alleles occur more often in people from specific geographic regions . New findings show that each human has on average 60 new mutations compared to their parents . </P>

How many alleles are in a human body
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