Genome complexity: our cells are a genome mosaic (Introduction)

by David Turell , Friday, July 19, 2019, 01:27 (1954 days ago) @ David Turell

The genome is various cell types differ in humans and I would guess call animals:

https://www.scientificamerican.com/article/the-human-body-is-a-mosaic-of-different-geno...

"The human body is a complex mosaic made up of clusters of cells with different genomes—and many of these clusters bear mutations that could contribute to cancer, according to a sweeping survey of 29 different types of tissue.

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"Tissue mosaics arise as cells accumulate mutations—from DNA errors that creep in during cell division, or because of exposure to environmental factors such as ultraviolet light or cigarette smoke. When a skin cell with a given mutation divides, it can create a patch of skin that is genetically different from its neighbors.

"Previous studies have found high levels of mosaicism in the skin, esophagus and blood. Those results were typically gleaned from sequencing specific genes in microscopic tissue samples.

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"Overall, the study found fewer examples of mosaicism in some types of tissue than would be expected on the basis of previous research. But the key, says Martincorena, is that the latest analysis demonstrated that mosaicism is present across a wide array of tissues.

"Tissues with a high rate of cell division, such as those that make up the skin and esophagus, tended to have more mosaicism than tissues with lower rates of cell division. Mosaicism also increased with age, and was particularly prevalent in the lungs and skin—tissues that are exposed to environmental factors that can damage DNA.

":A gene called TP53—which helps to repair DNA damage and is known as the guardian of the genome—was one of the most common mutation sites. Certain changes in TP53 are associated with cancer, but it might take additional mutations in other genes before cells give rise to tumors.

“'What we’re seeing are some of the earliest precancerous changes that are then going to accumulate more mutations,” says Erin Pleasance, who studies cancer genomics at the British Columbia Cancer Agency in Vancouver, Canada. “Eventually a small proportion of these may become cancer.'”

Comment: Part of the mosaicism is due to very different functions among our many cells. This study does not show that our germ cells show these genetic changes, but certainly our bodies are not t he ones we were born with.