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Humans are still evolving thanks to microgenes - Coggle Diagram
Humans are still evolving thanks to microgenes
Mesa N. 2023. Humans are still evolving thanks to microgenes. The Scientist Magazine. [accessed 2023 May 31].
https://www.the-scientist.com/news-opinion/humans-are-still-evolving-thanks-to-microgenes-70870
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Hiding Genes
First there was "junk" DNA.
Then we found these junk regions held over 155 genes.
Now we have microgenes, aka short open reading frames (sORFs)
They average only ~300bp.
Most genes fall between 10,000 and 15,000bp.
Disabling these sORFs direcctly impeded cell growth.
They may be small, but they are necessary.
sORFs have been located in coding and noncoding portions of DNA.
Of sORFs occuring in coding regions, 155 were determined to occur across vertebrates
40 were required for proper cellular development.
3 were pathological markers. 1 was associated with cardiac muscle in chimps and humans, but not gorillas.
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These sORFs developed from noncoding regions, not homologous duplication.
It is believed that these coding sORFs produce "proto-proteins."
Proto-proteins are small experiment that cells/tissues are "expirmenting" with.
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These 155 sORFs come from only two cell lines.
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Response
This was rather interesting
Size of Microgenes (1)
To think that a coding gene could only be 300bp long is somewhat amazing
300bp means 100 codons and 100 amino acids in the protein
Seeing as the smallest protein catalogued is 44 amino acids (Oyama et al 2004), 100 amino acids is not outlandish, but still surprising.
Oyama M, Itagaki C, Hata H, Suzuki Y, Izumi T, Natsume T, Isobe T, Sugano S. 2004. Analysis of small human proteins reveals the translation of upstream open reading frames of mRNAs. Genome Res. 14(10b):2048–2052. doi:10.1101/gr.2384604.
Source of Microgenes (2)
All through genetics, we were told of orthologs and paralogs. Random insertions were discussed, but nothing like the transformation of noncoding regions to coding regions.
This could be a great topic to introduce with CRISPR and CAS.
Making Sense (3)
The thought of cells "experimenting" with proteins sounds terrifying and should not suprisingly lead to diseases.
However, this is exactly what we see within B lymphocytes.
During a primary immune response, the immune system has yet to perfect its plan of attack on the pathogen.
As a result, B-cells produce IgM, a pentamer antibody with 5 variable regions (Marieb and Hoehn 2016).
This sounds a lot like the B-cells experimenting with antibody binding sites to best match the "new" pathogen's antigenic determinants.
Marieb EN, Hoehn K. 2016. Human anatomy & physiology. 10th ed. New York (NY): Pearson; p. 771-806.