Genome complexity: limiting rogue DNA errors (Introduction)

by David Turell , Wednesday, December 21, 2016, 15:50 (2895 days ago) @ David Turell

In preparing for reproduction there are mechanisms to prevent the transmission of DNA error segments. The mechanism os also present in somatic tissue:

http://phys.org/news/2016-12-rna-pathway-key-role-health.html

"Humans and other animals carry rogue sequences of DNA in their genomes called transposable elements (TEs). To prevent passing TEs to their offspring, they employ the piRNA pathway in their reproductive organs to block the elements from being active in their sperm and eggs. With a new study in flies, Brown University biologists are the first to show that the anti-TE activity of the piRNA pathway also operates in a normal non-reproductive body tissue, the fly fat body, and that it helps to sustain the life of the animal.

" It's required for normal health and longevity," said Dr. Stephen Helfand, senior author of the study in Nature Communications and a professor of biology at Brown University.

"Most previous reports of piRNA at work outside of reproductive organs were in cancer or stem cells, with one study suggesting it may also be present in a subset of adult fly neurons, but no one had ever measured its consequences in normal health and aging.

"In experiments led by Brown graduate student Brian Jones, the research team tracked several components of the pathway, such as the presence of piRNAs and the expression of associated "piwi" and "flamenco" genes, in the fat body tissue of flies. The fat body is akin to adipose and liver tissues in mammals and also contributes to flies' immune systems.

"Once the researchers confirmed that the piRNA pathway was active in a normal, mature body tissue, they conducted several experiments to see what happened in the flies when they knocked components of the pathway out. For example, with the piwi gene gone, flies had significantly fewer piRNAs than flies who had a copy.

"To see if a compromised pathway led to unchecked transcription of TEs, the researchers used a method that makes cells glow green when particular TEs move around within the genome. Flies without piwi lit up brightly.

"By other measures, the researchers found that piwi-lacking flies experienced increased DNA damage compared to flies with a working piwi gene, and flies lacking in either piwi or flamenco had less fat than controls. Flies without piwi succumbed to starvation more quickly, and flies with either of the genes knocked out lived considerably shorter lives than flies with a working copy of both genes.

"Specifically, about four in five flies with a working piwi gene were still alive at 60 days of age, but virtually all of the piwi-lacking flies were dead long before then. Among flies with a flamenco gene intact, about half were still alive at 60 days, while those lacking any flamenco had died off."

Comment: Reproduction whether it is sexual or simply cellular daughter cell production is vital to life continuing normally. Copy error protection had to be built in from the initiation of life itself. It could not have developed in a stepwise manner as Darwinism assumes.