Excision repair is a term applied to several DNA repair mechanisms. DNA repair refers to a collection of processes by which a cell identifies and corrects damage to the DNA molecules that encode its Genome.
Excision repair mechanisms that remove the damaged nucleotide replacing it with an undamaged nucleotide complementary to the nucleotide in the undamaged DNA strand. These include:
- Base excision repair (BER), which repairs damage due to a single nucleotide caused by oxidation, alkylation, hydrolysis, or deamination;
- Nucleotide excision repair (NER), which repairs damage affecting 2−30 nucleotide-length strands. Base excision repair (BER is a cellular mechanism that repairs damaged DNA throughout the cell cycle Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group Redox (shorthand for reduction-oxidation reaction describes all Chemical reactions in which atoms have their Oxidation number ( Oxidation state Alkylation is the transfer of an Alkyl group from one Molecule to another Hydrolysis is a Chemical reaction during which one or more water molecules are split into hydrogen and hydroxide ions which may go on to participate in further reactions Deamination is the removal of an Amine group from a Molecule. Nucleotide excision repair is a DNA repair mechanism DNA constantly requires repair due to damage that can occur to bases from a vast variety of sources including Nucleotides are Organic compounds that consist of three joined structures a nitrogenous base a Sugar, and a Phosphate group These include bulky, helix distorting damage, such as thymine dimerization and other types of cyclobutyl dimerization caused by UV light as well as single-strand breaks. Thymine is one of the four bases in the Nucleic acid of DNA that make up the letters ATGC A dimer is a Chemical or Biological entity consisting of two subunits called Monomers which are held together by either Intramolecular forces Pyrimidine dimers (cyclobutane dimer are pairs of Thymine and Cytosine bases in DNA that arise via Photochemical reactions Ultraviolet light A specialized form of NER known as Transcription-Coupled Repair (TCR) deploys high-priority NER repair enzymes to genes that are being actively transcribed;
- Mismatch repair (MMR), which corrects errors of DNA replication and recombination that result in mispaired nucleotides. Transcription is the synthesis of RNA under the direction of DNA Enzymes are Biomolecules that catalyze ( ie increase the rates of Chemical reactions Almost all enzymes are Proteins History See also History of genetics The existence of genes was first suggested by Gregor Mendel (1822-1884 who in the 1860s studied inheritance Transcription is the synthesis of RNA under the direction of DNA DNA mismatch repair is a system for recognising and repairing erroneous insertion deletion and mis-incorporation of bases that can arise during DNA replication and recombination DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded molecules Genetic recombination is the process by which a strand of genetic material (usually DNA; but can also be RNA) is broken and then joined to a different DNA molecule
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