The Uncertain Gene - 7

Proton Tunneling Induced Mutation

This series began with a specific focus on "proton tunneling" as a source of genetic mutation.

This series also considers generic results which could be caused by that specific event.

I am talking about the dynamic of machine mutation which takes place in the molecular machines that make up the cosmos of abiotic entities within cells, and more specifically the mutation taking place as a direct result of proton tunneling.

Therefore, this series also considers the probabilities that random machine mutation also has an impact on biotic entities, including human beings.

Further, since the human species is composed, like all cell based life, of both molecular machines and carbon based entities (both abiotic and biotic things), I noted earlier in this series that changes in molecular machines can cause changes at the biological level of cells too (cf. Putting A Face On Machine Mutation - 4).

A paper was published today in the journal Science which bears upon the subject matter of this series:

Genomic analyses of single human neurons—either from postmortem brains or those derived in culture—reveal a considerable degree of DNA copy number variation, according to a paper published today (October 31) in Science. It is likely that these genetic differences affect brain cell function, and they may even shape our personalities, academic abilities, and susceptibilities to neurological diseases.
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Hall has been able to sequence the genomes of 110 individual neurons from the postmortem brains of three individuals. He found that a striking 41 percent of the cells contained one or more copy number variations. Most of these were sub-chromosomal alterations—either deletions or duplications.

He and his colleagues also found similar copy number variations in neurons derived in culture from human induced pluripotent stem cells (iPSCs). Fred Gage and colleagues at the Salk Institute for Biological Studies in La Jolla, who collaborated on the paper, studied 40 individual iPSC-derived neurons using a recently developed single-cell microarray-based strategy, and found that 13 of the cells had unique changes to their genomes.

Interestingly, neural progenitor cells derived from the same iPSC lines did not exhibit such abundant diversity. This suggested that the genetic variation in neurons occurred only at later stages of differentiation. And that the variation developed in a short space of time—the seven weeks it took to differentiate neurons from neural progenitors. Furthermore, the results implied that genetic variations seen in adult postmortem brains were unlikely to be a mere side effect of aging.
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Indeed, Chun said it is possible that the observed genetic diversity in the brain may influence behavior, intelligence, and susceptibility to neurological and neuropsychiatric diseases. “I would say it is certain there will be functional consequences for at least some of these changes,” he explained.

(The Scientist, Our Fallen Genomes, Journal Science). The statement that "a striking 41 percent of the cells contained one or more copy number variations" is unexpected in brain cells.

That same unexpected discovery has been made in other areas where the human genome was found to be surprisingly variant:

From biology class to “C.S.I.,” we are told again and again that our genome is at the heart of our identity. Read the sequences in the chromosomes of a single cell, and learn everything about a person’s genetic information — or, as 23andme, a prominent genetic testing company, says on its Web site, “The more you know about your DNA, the more you know about yourself.”

But scientists are discovering that — to a surprising degree — we contain genetic multitudes. Not long ago, researchers had thought it was rare for the cells in a single healthy person to differ genetically in a significant way. But scientists are finding that it’s quite common for an individual to have multiple genomes. Some people, for example, have groups of cells with mutations that are not found in the rest of the body. Some have genomes that came from other people.

(The "It's In Your Genes" Myth - 2, emphasis added). Add to that the fact that most of the genetic material in us is microbial (The Human Microbiome Congress), and we do not have a workable handle on all of that, the discipline of microbiology is looking like a good place for college and university students to ponder --as future career paths.

Maybe they can tell us which used book store gives the most coin for old, out of date science textbooks (The Appendix of Vestigial Textbooks - 4).

The next post in this series is here, the previous post in this series is here.