Search results
Results from the WOW.Com Content Network
Prokaryotic DNA Replication is the process by which a prokaryote duplicates its DNA into another copy that is passed on to daughter cells. [1] Although it is often studied in the model organism E. coli, other bacteria show many similarities. [2] Replication is bi-directional and originates at a single origin of replication (OriC). [3]
The replication of DNA with a broken sugar-phosphate backbone is most likely facilitated by the homologous recombination proteins that confer resistance to ionizing radiation. The activity of PRR enzymes is regulated by the SOS response in bacteria and may be controlled by the postreplication checkpoint response in eukaryotes.
Eukaryotes initiate DNA replication at multiple points in the chromosome, so replication forks meet and terminate at many points in the chromosome. Because eukaryotes have linear chromosomes, DNA replication is unable to reach the very end of the chromosomes. Due to this problem, DNA is lost in each replication cycle from the end of the chromosome.
This can either involve the replication of DNA in living organisms such as prokaryotes and eukaryotes, or that of DNA or RNA in viruses, such as double-stranded RNA viruses. [3] Synthesis of daughter strands starts at discrete sites, termed replication origins, and proceeds in a bidirectional manner until all genomic DNA is replicated.
The AP endonucleases also participate in 3' end processing. Besides opening AP sites, they possess 3' phosphodiesterase activity and can remove a variety of 3' lesions including phosphates, phosphoglycolates, and aldehydes. 3'-Processing must occur before DNA synthesis can initiate because DNA polymerases require a 3' hydroxyl to extend from.
Strand slippage may also occur during the DNA synthesis step of DNA repair processes. Within DNA trinucleotide repeat sequences, the repair of DNA damage by the processes of homologous recombination , non-homologous end joining , DNA mismatch repair or base excision repair may involve strand slippage mispairing leading to trinucleotide repeat ...
The extent of proofreading in DNA replication determines the mutation rate, and is different in different species. [4] For example, loss of proofreading due to mutations in the DNA polymerase epsilon gene results in a hyper-mutated genotype with >100 mutations per Mbase of DNA in human colorectal cancers. [5]
DNA mismatch repair (MMR) is a system for recognizing and repairing erroneous insertion, deletion, and mis-incorporation of bases that can arise during DNA replication and recombination, as well as repairing some forms of DNA damage.