Key Terms for DNA Damage and Repair

alkylation - The process in which electrophiles attack the negative charge centers on the phosphate or the partial negative charge on negative bases of a nucleotide, usually adding carbon-containing groups called alkyl groups.

carcinogens – Cancer-causing agents.

clastogen – Ionizing radiation that breaks chromosomes; is also referred to as a mutagen, or mutation-causing substance.

dimer (protein) – A complex of two polypeptides.

DNA photolyase – The enzyme responsible for photoreactivation repair of DNA damage.

electrophile – A substance that seeks the center of negative charge in other molecules and binds to them.

error-prone bypass – One of the mechanisms dealing with DNA damage that avoids the damaged area without replacing it.

excinuclease – A more general term for the enzyme system that catalyzes nucleotide excision repair.

excision repair – Mechanism that removes damaged bases by deleting the damaged DNA and replacing it with fresh DNA.

free radicals – Chemical substances with an unpaired electron.

gamma rays – Very high energy radiation that ionizes cellular components. The ions can then cause chromosome breaks.

microsatellites – Tandem repeats of 1- to 4-bp sequences in DNA.

mismatch repair – The correction of a mismatched base incorporated by accident – in spite of the editing system – into newly synthesized DNA.

photoreactivation – Mechanism of repair of damage to DNA using exposure to light to activate enzyme activity.

ultraviolet radiation – relatively low energy radiation found in sunlight. Causes thymine dimers in DNA.

X rays – High energy radiation that ionizes cellular components. The ions then can cause chromosome breaks.

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