Formerly the upper classes, especially the kings, married each other in order to preserve their "pure" blood, strengthen the line of succession and maintain power in the family. What they did not know is that this "purity" conceived heirs with a high probability of suffering from diseases. Have you ever wondered why?
The main reason is genetic diversity. Inbreeding in real families reduced the genetic diversity of the children since, if an individual has a child with a relative, the paternal and maternal alleles will be very similar and this similarity will be strengthened generation after generation.
And you may wonder, what does genetic diversity have to do with diseases? Much. There are numerous diseases that follow a recessive inheritance pattern, that is, for the disease to manifest both alleles ("letritas" inherited from the mother and part of the father) must be risk alleles, "defective alleles" ”.
For this reason, if your genetic diversity is high, the probability that you inherit two "defective" alleles decreases. And one way to quantify genetic diversity is with the heterozygosity ratio (available in the section on Ancestry).
The heterozygosity ratio (SNPs heterozygous / homozygous non-ancestral SNPs) has a fundamental advantage over other diversity metrics. Normalization (splitting) provides consistency between different regions of the chromosome and between different genotyping platforms. However, heterozygosity ratios vary depending on the ancestry of each individual. For this reason, in the reports of ADNTRO we show a reference panel with which you can compare your genetic diversity based on your ancestors.