Genome complexity: DNA 3-D importance in replication (Introduction)

by David Turell , Tuesday, January 01, 2019, 18:03 (1941 days ago) @ David Turell

It is now shown that cells can rearrange DNA for replication:

https://www.sciencedaily.com/releases/2018/12/181227150644.htm

" Taylor demonstrated how different segments of chromosomes duplicate in the late 1950s and published more than 100 papers on chromosome structure and replication. Roughly 60 years later, Gilbert determined how replication was regulated.

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"Gilbert and Sima examined a single segment of the DNA in the highest possible 3D resolution and saw three sequences along the DNA molecule touching each other frequently. The researchers then used CRISPR, a sophisticated gene editing technology, to remove these three areas simultaneously.

"And with that, they found that these three elements together were the key to DNA replication.

"'Removing these elements shifted the segment's replication time from the very beginning to the very end of the process," Gilbert said. "This was one of those moments where just one result knocks your socks off."

"In addition to the effect on replication timing, the removal of the three elements caused the 3D structure of the DNA molecule to change dramatically.

"We have for the first time pinpointed specific DNA sequences in the genome that regulate chromatin structure and replication timing," Sima said. "These results reflect one possible model of how DNA folds inside cells and how these folding patterns could impact the hereditary materials' function."

"Greater understanding of how DNA replication is regulated opens new paths of research in genetics. When replication timing is altered -- as it was in Gilbert and Sima's experiment -- it can completely change how the genetic information of a cell is interpreted. This could become crucial information.

"'If you duplicate at a different place and time, you might assemble a completely different structure," Gilbert said. "A cell has different things available to it at different times. Changing when something replicates changes the packaging of the genetic information.'"

Comment: Just as Shapiro shows, DNA can be edited by cells. The implication is that this ability was present when bacteria appeared early in evolution. 3-D DNA is a major key to the amazing variations in controls DNA can exert just by its own 3-D relationships and how they change. Just where are the instructions to guide DNA contortions? Probably in other parts of the specific DNA. This is obviously key evidence as to how as few as 22,000 genes make a complex human.