Genome complexity: protecting DNA integrity in reproduction (Introduction)

by David Turell , Sunday, November 04, 2018, 15:00 (2212 days ago) @ David Turell

In this study DNA protections are reviewed as sperm and egg produce a new individual:

https://phys.org/news/2018-11-invading-genes-thwarted.html

"Since Carnegie Institution's Barbara McClintock received her Nobel Prize on her discovery of jumping genes in 1983, we have learned that almost half of our DNA is made up of jumping genes—called transposons. Given their ability of jumping around the genome in developing sperm and egg cells, their invasion triggers DNA damage and mutations. This often leads to animal sterility or even death, threatening species survival. The high abundance of jumping genes implies that organisms have survived millions, if not billions, of transposon invasions. However, little is known about where this adaptability comes from. Now, a team of Carnegie researchers has discovered that, upon jumping gene invasion, reproductive stem cells boost production of non-coding RNA elements (piRNA) that suppress their activity and activates a DNA repair process allowing for normal egg development.

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"They found that reproductive stem cells use a novel adaptive response to "rapidly tame" the invading elements by activating the so-called DNA damage checkpoint. This is a process that activates a pause in the cell cycle, before cell division, to repair damaged DNA. A checkpoint component, called Chk2, was found to be key. This pause in the repair process amplified the production of piRNA—those non-coding RNA elements that silence the jumping genes. They found that this pause period is necessary for adaptation and for permanently silencing the invading jumping genes, which allowed for normal egg production that could begin within four days.

"'Jumping gene invasion triggers catastrophic genomic instability in all organisms," remarked Zhao Zhang. "They greatly reduce the viability or fertility of the invaded animals and can lead to a population crisis. We believe that the ability of reproductive stem cells to rapidly adapt and restore fertility in this manner allows species to resist such a population crash. This mechanism is a lynchpin to species survival.'" (my bold)

Comment: My bolded sentence makes that obvious point that design is necessary from the beginning of sexual reproduction. Since transposons cause such trouble, control mechanisms had to be present from the beginning.