Tracking a network of 100,000 mutants

What fundamentally sets a human being apart from every other living creature comes down to differences in DNA sequences—a set of genetically-inherited molecules found in every cell of every organism. These differences have ...

"We've managed to experimentally show, for the first time, a concept about mutation and evolution that has previously only been theoretically predicated," said Prof. Yohei Yokobayashi, who leads to Nucleic Acid Chemistry and Engineering Unit at the Okinawa Institute of Science and Technology Graduate University (OIST). "It's called a neutral network and it's thought to be vital for increasing diversity in a population." This research was published in Nature Communications . Genes, made up of DNA base pairs, contain the instructions needed to create proteins, and lead to the proper care and maintenance of a cell. For the instructions to be carried out, the DNA must first be transcribed into RNA. Thus, RNA is like a reflection of DNA.

There are four standard base pairs for RNA and DNA. For RNA, these are A, G, C, and U. Prof. Yokobayashi explained the concept of a neutral network by giving an example of a simplified sequence of RNA bases. "Say, the RNA sequence AAAAAAA mutates to AAAUAAA, which then mutates to GAAUAAA. The first variant is connected to the second one, which is connected to the third by just one single mutation. If these mutations maintain the same fitness, the organism might survive, and the mutation might be inherited by future generations. This increases the overall diversity, and diversity is essential for a species to adapt to changes in the environment."

This image is a simplified representation of the classic landscape of fitness. If a mutation occurs, the organism will normally fall from the top of the peak into the ditch, losing fitness and likely not surviving or reproducing. Credit: OIST Read more

This image is a simplified representation of a landscape of fitness when there is a neutral network. When there is a mutation, the fitness is maintained. Credit: OIST Read more

Mutations must maintain a similar fitness level compared to the one before and after them if diversity is to increase. If the mutation negatively impacts the variant, then the pathway to reach other variants will not be accessible. The above image shows a short sequence and the mutations that come from it. As can be seen, either the mutations maintain the same fitness level as the one before them and go on to form new mutants, or they are of lower fitness level and die out. Please note that the sequence is just an example and does not specifically relate to this research. Credit: OIST Read more