Heavy weight: the Cell overwrites the textbook and takes the first DNA random copy
Almost all life on earth is based on DNA replication or replication.
Understanding the process of DNA replication has led to many important discoveries in biology and medicine.
Now, for the first time, scientists have seen the full steps of a single DNA replication, with some striking findings - DNA replication is more random than we thought.
1. Amazing findings
At the university of California, Davis, and university of California, Davis, comprehensive cancer research center in microbiology and molecular genetics distinguished professor Stephen Kowalczykowski said: another way to see DNA replication brings new discovery.
The work published in Cell on June 15, titled "the Independent and Stochastic Action of DNA Polymerases in the Replisome", journal of co-author James Graham is at the university of California, Davis, Sloan caitlin postdoctoral researcher at the cancer center.
Using sophisticated imaging techniques and a great deal of patience, the researchers looked at the DNA of e. coli and measured how quickly the enzyme mechanism worked on different chains.
They made a miraculous video of a single DNA molecule replicating a near-high-definition, uncoded image.
2.Basis for DNA replication
The DNA double helix is made of two reverse complementary strands.
Each chain is made of A series of bases A, T, C, and G, and the pairs of rules between chains are: A and T, C and G.
The first step of replication is to unscrew the double helix into two single chains.
Then the primers attach the primer to each strand of the beginning of the replication, and then the DNA polymerase attaches to the primer and moves along the chain, adding a new base to form a new double helix.
The DNA polymerase ACTS differently on the two strands of DNA, which run in the opposite direction.
On the leading chain, the DNA polymerase can move continuously, leaving a new double stranded DNA.
On the lagging strand, the DNA polymerase must move at first, attach, produce a short strand of double stranded DNA, and then fall off and start again.
The conventional view is that the DNA polymerase in the leading and lagging chains works in a way that doesn't lead to the other.
If that happens, it will produce a lot of damaged DNA fragments that cause mutations.
3.How is a single DNA replication discovered
The researchers used a short tail to attach the circular DNA to a slide.
The tail lengthened as the copying machine spun around.
They can control replication by adding chemical fuel (NTPs) and use fluorescent dyes attached to double stranded DNA to lighten the synthetic chain.
Finally, the whole set is in the moving room, and the DNA strand stretches like a banner in the breeze.
The study found that replication termination was unpredictable, and when replication was restarted it could even change the speed of replication.
In the lens, the lag chain stops running, but the leading chain continues to grow (because the dye is not attached to the single strand of DNA, so it is shown as a black area in the light chain).
Sometimes one of the chains suddenly begins to replicate at 10 times normal speed, without any regularity.
In addition, due to lack of coordination, DNA can even kick the dissolving enzyme to halt replication to make the DNA polymerase catch up.
This random reproduction is a new discovery of DNA replication, and we're going to rethink the biochemical process.
This is a paradigm shift, completely different from what is in the textbook.