What DNA repair mechanism is used to double-strand breaks in G2 phase?
What DNA repair mechanism is used to double-strand breaks in G2 phase?
homologous recombination
DNA non-homologous end joining (NHEJ) and homologous recombination (HR) function to repair DNA double-strand breaks (DSBs) in G2 phase with HR preferentially repairing heterochromatin-associated DSBs (HC-DSBs).
How does homologous recombination repair double-strand breaks in DNA?
Double-strand breaks can be repaired through homologous recombination, polymerase theta-mediated end joining (TMEJ) or through non-homologous end joining (NHEJ). NHEJ is a DNA repair mechanism which, unlike homologous recombination, does not require a long homologous sequence to guide repair.
Which DNA repair mechanism uses the sister chromatid as a template for repairing double-strand breaks?
recombination
In mitotically dividing cells, recombination is used primarily for DNA repair, with the major template for repair being the sister chromatid.
What is double-strand break model?
In the double-strand-break model, the region corresponding to the original gap now has the sequence of the donor duplex in both molecules. Part of one duplex molecule has been converted to the sequence of the other (the recipient, initiating duplex has been converted to the sequence of the donor).
What causes a double strand break in DNA?
The genome of a cell is continuously damaged, which is inevitable because DNA damage often arises as a result of normal cellular processes. The result is double-strand breaks (DSBs) in the chromosome. A DSB can also be caused by environmental exposure to irradiation, other chemical agents, or ultraviolet light (UV).
What are possible negative consequences of breaking apart human DNA?
DNA may be modified in a variety of ways, which can ultimately lead to mutations and genomic instability. This could result in the development of a variety of cancers including colon, breast, and prostate.
What causes DNA double strand break?
What is the simplest DNA repair system?
The simplest and most accurate repair mechanism is the direct reversal of damage in a single-step reaction. The enzymatic photoreactivation of a cyclobutane pyrimidine dimer (CPD), which is the major product of UVB and UVC radiation, by DNA photolyase is the prototype of this type of reaction.
What happens if a double strand break is not repaired?
By-products of the cell’s own metabolism such as reactive oxygen species can damage DNA bases and cause lesions that can block progression of replication. The result is double-strand breaks (DSBs) in the chromosome. And, if not repaired correctly, DSBs can cause deletions, translocations, and fusions in the DNA.
How many double strand breaks a day?
The best known of such lesions is the DNA double-strand break (DSB). DNA DSBs occur in any given cell in the order of 10 to 50 per cell per day, depending on cell cycle and tissue (Vilenchik and Knudson, 2003).
How do you fix a double strand break?
DNA double-strand breaks are repaired by means of two main mechanisms: nonhomologous end joining and homologous recombination (see Figure 1). Both mechanisms operate in all eukaryotic cells that have been examined but the relative contribution of each mechanism varies.
What are 3 ways DNA gets damaged?
DNA bases can be damaged by: (1) oxidative processes, (2) alkylation of bases, (3) base loss caused by the hydrolysis of bases, (4) bulky adduct formation, (5) DNA crosslinking, and (6) DNA strand breaks, including single and double stranded breaks. An overview of these types of damage are described below.
How are double strand DNA breaks repaired in cells?
Double-strand DNA breaks are common events in eukaryotic cells, and there are two major pathways for repairing them: homologous recombination (HR) and nonhomologous DNA end joining (NHEJ). The various causes of double-strand breaks (DSBs) result in a diverse chemistry of DNA ends that must be repaired.
How are DSBs repaired in the eukaryotic cell?
Two major pathways have evolved to repair DSBs: HR (homologous recombination) and NHEJ (non-homologous end-joining). Depending on the context in which the break is encountered, HR and NHEJ may either compete or co-operate to fix DSBs in eukaryotic cells.
How does NHEJ work to repair DNA damage?
Unlike repair pathways for more defined lesions, NHEJ repair enzymes act iteratively, act in any order, and can function independently of one another at each of the two DNA ends being joined.
Why is NHEJ important for the repair of DSBs?
NHEJ is critical not only for the repair of pathologic DSBs as in chromosomal translocations, but also for the repair of physiologic DSBs created during variable (diversity) joining [V (D)J] recombination and class switch recombination (CSR).