The SNAP hypothesis – Refining the theory of evolution

Hyperaxion Mar 4, 2020

Researchers at Uppsala University, Sweden, put forward a hypothesis that tries to explain how genes move on chromosomes. The article was published in PLOS Genetics.

The Theory of Evolution is one of the main subjects of biology, since it helps us to understand the physiology of living beings and their relationship with the environment. Biological evolution refers to changes that populations of living organisms may suffer over time.

The main evidence of the evolutionary aspect of the species is found in fossils, preserved remains of animals and sedimented plants in the most varied places around the world.

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In the reproductive process, during DNA duplication, the DNA polymerase enzyme can make mistakes resulting in a change, or loss, in the nucleotide sequence, producing new alleles. These are called mutations, and they contribute to variability in the process of natural selection.

What is still a mystery, however, is that the location of genes on chromosomes also tends to change over time. This is what scientists at Uppsala University try to explain with the SNAP hypothesis.


When analyzing the chromosome of bacteria, the scientists noticed that duplication of sections tends to occur very often and, unless they are selected, they are lost. For duplication to be preserved, the bacteria must live in an environment in which having this specific gene in double is an evolutionary advantage.

Comparison of standard hypothesis of genomic rearrangements and the SNAP model.
Comparison of standard hypothesis of genomic rearrangements and the SNAP model. (Credit: PLOS Genetics).

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Duplications typically carry hundreds of genes, even though only one of them is selected. According to Gerrit Brandis and Diarmaid Hughes, the scientists responsible for the hypothesis, this causes mutations to accumulate in genes that have not been selected, even in genes with a single copy on the chromosome.

In this way, bacteria have a large number of duplicated genes, which is generally a bad thing, and mutations that end up deleting those genes become an evolutionary advantage and are selected. Scientists argue that through this process of losing unnecessary duplicate genes, the order of the remaining genes may change over time.


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