2019-10-21 07:37:40
To date, thousands of genomic association studies have been published to find genes associated with diseases, conditions or the most varied human abilities, such as intelligence, personality or homosexuality.
The human genome is made up of about three billion nucleotides, the “letters” of the ADN. Except for twin brothers, who have inherited identical genomes, humans differ from each other by up to 1% of those “letters”, that is, by up to 30 million letters in each copy. These differences in single letters are called in the genetic language SNPs (single nucleotide polymorphisms).
It is estimated that Humanity as a whole has around 335 million SNPs, although each of us owns only 30 million at most. Obviously, not all SNPs appear with the same frequency.
chips ADN can be used to search SNPs associated with a disease (such as Alzheimer’s) or a certain condition (such as height or intelligence). This is what complete genomic association studies pursue.
In some cases a disease may be caused by mutations in a single gene. In this case, the disease is said to be monogenic. However, the vast majority of human characteristics, such as intelligence or outgoing personality, involve numerous genes. In this case the disease, or condition, is said to be polygenic.
Genomic association studies attempt to find out which genes may be responsible for a disease or condition and estimate how many there are. These studies are very extensive. For example, in a recent study on homosexuality, the genome of nearly half a million people classified as homosexual was studied.
Genomic association studies generally reveal tens or hundreds of gene variants. However, none of them is 100% responsible. For this reason, scientists estimate the importance of all genes by adding the frequencies of each gene variant identified in the study as being associated with the disease or condition. This is what, for lack of a better definition, I call the polygenic ratio. This polygenic quotient is a numerical value that can be calculated for each person and is an estimate of the influence that the gene variants that this person possesses can have on whether or not that person develops a disease or a certain personal quality. This is what scientists have done for homosexuality, which, as we have said, cannot depend on a single gene, but is influenced by many, in addition to factors that are not directly genetic.
Jorge Laborda, October 20, 2019
Reference:
Andrea Ganna et al (2019). Large-scale GWAS reveals insights into the genetic architecture of same-sex sexual behavior.
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Kilo of Science Volume I. Jorge Laborda
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