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Population Genetics

Population Genetics is a branch of Genetics that studies the genetic composition of the populations and how they change through time. In these terms, a population has a determined allelic composition as a result of the different evolutionary processes experienced in the past. Knowing the alleles and the changes in their frequencies of a particular population in a determined period give us an idea of the origin and the phenomena a population could have suffered. 

Roughly, population genetics helps to explain what determined the actual composition of a population, something like their “genetic history.” 

An example of how genetics help to explain the history of a population is present in one of our latest papers. In it, we see how the Haplotypes and Haplogroups found in the aboriginal population of the Canary Islands allow us to track their origins back to North Africa and identify some of the mixture and evolution processes these populations have had before colonizing the Archipelago. We can also observe a differentiated evolution from the population of the different islands once established in the new territories. 

Among the most common genetic variants that population genetics study we find: 

  1. SNP (Single Nucleotide Polymorphism): It is a polymorphism that occurs only in one nucleotide of the DNA chain. They are the most frequent changes in the population. 
  2. INDEL: Polymorphisms characterized by the insertion or deletion of a few nucleotides within the genome.
  3. STR (Simple Tandem Repeats): Polymorphisms that differ in the number of repetitions of a short sequence of nucleotides (2-6 nucleotides). 

*Allele: Each one of the alternative ways of a genetic variant. When it is over 1% in a population, it is usually called genetic polymorphism. e.g., in an SNP from a determined region of the genome, the most common allele in the population one is A, while in the population two, it can be C. 

*Haplotype: Group of alleles that are inherited together as a consequence of their closeness within the genome. Depending on their nucleotide similarity, they are grouped into haplogroups * to form a phylogenetic tree. All the haplotypes of a haplogroup share a common ancestor, making it possible to trace the origin (evolutionary and geographic) of the studied population going back in the tree.

* Allelic frequency: Relative proportion of alleles in a population.