1. Removal of DNA damages and restoration of the continuity of the DNA duplex
2. Activation of a DNA damage checkpoint, which arrests cell cycle progressions so as to allow for repair and prevention of the transmission of damged or incompletely replicated chromosomes.
3. Trancriptional response, which causes changes in the transciption profile that may be beneficial to the cell
4. Apoptosis, which eliminate heavily damged or deregulated cells (Programmed cell death)
Explanation:
Firstly, Mutation is referred to as alternation in DNA. Mutations may be caused as a result from mistakes made during DNA replication. Also, chemicals or physical forces can damages a segment of DNA before it is replicated. Unless these errors are detected and corrected before the next replication, they may be passed on to future cells or could even prevent the DNA from being copied at all. This is to say that the DNA needs to be in be in a good condition as possible before it is replicated. When a cell of the body is severly damaged, it may not possible or easy to repair all the error. In such cases, substatial changes in cell function and even destructive cancers can occur. Mutation can be spontenous or induced.
When we talk about spontaneous, they are rare mutations are rare and results from errors in DNA replicatlon. Induced mutations are caused by environmental factors, such as radiation, chemical substances, etc. The frequency of such mutations depends on the type and duration of agent which is mutagen.
Damges to DNA induces several cellular responses that enable the cell either to eliminate or to activate a programmed cell death process, presumably to eliminate with potentially castrophic mutations.
There are several DNA damage response reaction in a cell such as:-
1. Removal of DNA damages and restoration of the continuity of the DNA duplex
2. Activation of a DNA damage checkpoint, which arrests cell cycle progressions so as to allow for repair and prevention of the transmission of damged or incompletely replicated chromosomes.
3. Trancriptional response, which causes changes in the transciption profile that may be beneficial to the cell
4. Apoptosis, which eliminate heavily damged or deregulated cells (Programmed cell death)
These are all procesess or mechanism to prevent mutation/ repairing linked with cell cycle.
The cycle cannot proceed without a series of successive events occurring. If there is an event failure, then the cell arrests at defined checkpoints to allow adjustments to be made. The most notable checkpoints occur at the G1-S and G2-M transition points. The G1-S checkpoint allows the cell to repair any DNA damage before it is copied in the S-phase, to prevent mutations becoming fixed in the genetic material. The second, G2-M checkpoint allows the cell to ensure that the chromosomes are arranged correctly prior to segregation to the daughter cells. In response to DNA damage, checkpoints arrest the cell cycle in order to provide time for DNA repair. DNA damage checkpoints are positioned before the cell enters S phase (G1-S checkpoint) or after DNA replication (G2-M checkpoint) and there appears to be DNA damage checkpoints during S and M.An important part of the cellular response to DNA damage is checkpoint activation checkpoint kinases CHK1 and CHK2 phosphorylate key proteins to elicit cell-cycle blocks. Inhibiting these kinases to sensitize the damage DNA, because in the absence of checkpoints and efficient DNA repair, there is a possibility of response switching to cell death or senescence.
