What happens in the body when DNA is damaged?

The DNA in the cell is damaged by tens of thousands of times per day and restored. At that time, what kind of things are done in the body is summarized in the movie "What happens when your DNA is damaged?"

What happens when your DNA is damaged? - Monica Menesini | TED-Ed
http://ed.ted.com/lessons/what-happens-when-your-dna-is-damaged-monica-menesini

What happens when your DNA is damaged? - Monica Menesini - YouTube


Even DNA from just one cell will receive tens of thousands of damage a day.


In other words, it means that hundreds of trillion times more DNA errors are occurring every day in all cells.


The total number of errors is as high as 100 ky.


The work of DNA is to provide a blueprint for making proteins necessary for cell function.


However, if DNA is damaged, serious problems such as cancer will occur.


This "DNA error" appears in various forms. SometimesnucleotideIt is also damaged.



Also, nucleotide mismatches may cause mutations.


Single chainYaDouble strandThe defective part may interfere with the replication of the DNA or cause an error in the base sequence.


However, there are things that should be called "repair centers" in the cells ......


Repair such errors with special enzymes. Different enzymes react according to the type of damage.


A single nucleotide has one base.


During DNA replication, an enzyme called DNA polymerase takes in matched bases,Template chainIt is supposed to make a base sequence on.


Adenine is thymine and guanine is hydrogen bonded to cytosine, respectively.


A mismatch will occur at a rate of about one hundred thousandths, but the enzyme immediately notices an error ... ...


Replace the wrong nucleotide with the correct nucleotide.


The second repair enzyme repairs the mismatch even if it is not replaced.




By performing a two-step check, the number of mismatches will be reduced to approximately one billionth of a degree.


However, DNA may be damaged even after replication.


Many molecules are affected to cause nucleotides to undergo chemical changes.


There are also environmental factors, for example, substances contained in tobacco smoke.


Hydrogen peroxide which is naturally present in cells is also one factor.


In the case of frequent chemical changes, specific enzymes restore damage.


Cells also have a general repair process, and if damage is only 1 baseBase excision repairRestoration is done in the process.


An enzyme removes damaged bases ... ...


Other enzymes replace with new nucleotides.


Damage from ultraviolet rays may cause adjacent nucleotides to connect and distort the double helical structure of DNA.


In case of such damage, remove the chain of about 24 nucleotides and replace it with a new oneNucleotide excision repairIs done.


In the case of high frequency radiation such as gamma rays and X rays, the chain of the DNA skeleton will be broken.


Although it is dangerous that it is dangerous to double-strand break, even single-strand breakage is sufficiently dangerous.


There is a danger that the cell will die.


Repair of common double-strand breaks,Homologous recombinationWhenNonhomologous end joinIt is done in the process of.


"Homologous recombination" uses undamaged portions of similar DNA as a template.


Combining damaged DNA and undamaged DNA ... ...


Replace the nucleotide sequence and fill the vacant area.


And make it a complete duplex.


One "nonhomologous end join" does not use a template. Remove nucleotides from the tip of the broken protein ... ...


Combine the tips.



However, it is not as accurate as homologous recombination.


Although genes may confuse or move about,Sister chromatidIt is useful when there is not.


Changes in DNA are not only bad, but there are also useful mutations that evolve species. Nonetheless, if anything I want to maintain DNA.


Deficiency of DNA repair gene is associated with premature aging and many cancers.


Actually, "fountain of the eternal youth" is in the body of everyone, it is doing the work of billions times a day.