This enzymes involved in dna replication pdf a featured article. Click here for more information. As a consequence, the DNA repair process is constantly active as it responds to damage in the DNA structure. The rate of DNA repair is dependent on many factors, including the cell type, the age of the cell, and the extracellular environment.
The DNA repair ability of a cell is vital to the integrity of its genome and thus to the normal functionality of that organism. DNA damage repair and protection. 10,000 to 1,000,000 molecular lesions per cell per day. While this constitutes only 0.
These modifications can in turn disrupt the molecules’ regular helical structure by introducing non-native chemical bonds or bulky adducts that do not fit in the standard double helix. The replication of damaged DNA before cell division can lead to the incorporation of wrong bases opposite damaged ones. DNA base is stitched into place in a newly forming DNA strand, or a DNA base is skipped over or mistakenly inserted. Damage caused by exogenous agents comes in many forms. X-ray damage and oxidative damage are examples of induced damage. Whenever a cell needs to express the genetic information encoded in its nDNA the required chromosomal region is unravelled, genes located therein are expressed, and then the region is condensed back to its resting conformation.
Therefore, the induction of senescence and apoptosis is considered to be part of a strategy of protection against cancer. It is important to distinguish between DNA damage and mutation, the two major types of error in DNA. DNA damage and mutation are fundamentally different. DNA damage can be recognized by enzymes, and thus can be correctly repaired if redundant information, such as the undamaged sequence in the complementary DNA strand or in a homologous chromosome, is available for copying.
If a cell retains DNA damage, transcription of a gene can be prevented, and thus translation into a protein will also be blocked. Replication may also be blocked or the cell may die. In contrast to DNA damage, a mutation is a change in the base sequence of the DNA. A mutation cannot be recognized by enzymes once the base change is present in both DNA strands, and thus a mutation cannot be repaired. At the cellular level, mutations can cause alterations in protein function and regulation.