DNA Repair system
Cells have several enzymes that responsible for repairing damaged DNA. and each one of these enzymes works on only on a specific type or types of damaged DNA.
Also these enzymes go under genetic control and they may undergo mutations
DNA damage happens all the time, it occurs spontaneously and in all cells
For example on these enzymes :
1-DNA POLYMERASE have 3 activities{DNA polymerase , 3’ 5’ exonuclease and Removal of RNA primers by 5’→3’ exonuclease activity
the function of 3’ 5’ exonuclease works if the bases does not match so the 3’ 5’ exonuclease function will remove it and the polymerase function remake the strand
The function of 5’ 3’ exonuclease works to remove the RNA primers
2- removal of T=T dimers by DNA photolyase
T=T Dimers are A common Photoproduct of UV treatment of DNA in vivo and in vitro is an intra-strand dimer formed between adjacent thymines
-------------------------------------------------------------------
There are two major types of mutation :-
1- single strand break
which is easily repaired by repair enzymes using the other strand as the templat
2- Double-Stranded Break
this kinds of Breaks cannot be repaired and lead to mutation during mitosis and also Often lethal because can't be resealed by ligase so degraded by nucleases
The efficient repair of DSBs is crucial in maintaining genomic integrity, cellular viability, and the prevention of tumorigenesis.
That is enough for today. I will talk about the mechanisms of DNA repair in soon as possible
----------------------------------------------------------------------
Cells have several enzymes that responsible for repairing damaged DNA. and each one of these enzymes works on only on a specific type or types of damaged DNA.
Also these enzymes go under genetic control and they may undergo mutations
DNA damage happens all the time, it occurs spontaneously and in all cells
For example on these enzymes :
1-DNA POLYMERASE have 3 activities{DNA polymerase , 3’ 5’ exonuclease and Removal of RNA primers by 5’→3’ exonuclease activity
the function of 3’ 5’ exonuclease works if the bases does not match so the 3’ 5’ exonuclease function will remove it and the polymerase function remake the strand
The function of 5’ 3’ exonuclease works to remove the RNA primers
2- removal of T=T dimers by DNA photolyase
T=T Dimers are A common Photoproduct of UV treatment of DNA in vivo and in vitro is an intra-strand dimer formed between adjacent thymines
-------------------------------------------------------------------
There are two major types of mutation :-
1- single strand break
which is easily repaired by repair enzymes using the other strand as the templat
2- Double-Stranded Break
this kinds of Breaks cannot be repaired and lead to mutation during mitosis and also Often lethal because can't be resealed by ligase so degraded by nucleases
The efficient repair of DSBs is crucial in maintaining genomic integrity, cellular viability, and the prevention of tumorigenesis.
That is enough for today. I will talk about the mechanisms of DNA repair in soon as possible
----------------------------------------------------------------------
تعليق