What kind of DNA lesion does UV energy cause?

cyclobutane pyrimidine dimers
UV radiation causes two classes of DNA lesions: cyclobutane pyrimidine dimers (CPDs, Figure 1) and 6-4 photoproducts (6-4 PPs, Figure 2). Both of these lesions distort DNA’s structure, introducing bends or kinks and thereby impeding transcription and replication.

What fixes UV damage in DNA replication?

DNA Repair The genetic lesions produced by UV radiation are often repaired soon after they are formed, through a process called nucleotide excision repair. A nuclease enzyme recognizes and removes a segment of DNA containing the lesion. Then, the polymerase inserts the correct bases and ligase seals the gap.

How many DNA lesions do UV radiation cause daily?

While the ozone layer absorbs the most dangerous part of the solar UV spectrum (UV-C), residual UV-A and UV-B in strong sunlight can induce ~100,000 lesions per exposed cell per hour. Ionizing radiation (IR) also generates various forms of DNA damage, the most toxic of these being DSBs5.

What is error free DNA repair?

The postreplication repair pathway (PRR) is composed of error-free and error-prone sub-pathways that allow bypass of DNA damage-induced replication-blocking lesions. The error-free sub-pathway is also used for bypass of spontaneous DNA damage and functions in cooperation with recombination pathways.

How does UV radiation damage DNA quizlet?

UV light damages the DNA of exposed cells by causing bonds to form between adjacent pyrimidine bases, usually thymines, in DNA chains. The thymine dimers inhibit correct replication of the DNA during reproduction of the cell.

What is the most common type of DNA damage caused by ultraviolet UV radiation?

UV radiation induces two of the most abundant mutagenic and cytotoxic DNA lesions such as cyclobutane-pyrimidine dimers (CPDs) and 6-4 photoproducts (6-4PPs) and their Dewar valence Isomers.

What causes DNA damage?

DNA damage can be subdivided into two types: (1) endogenous damage caused by reactive oxygen species (ROS) that are derived from metabolic byproducts and (2) exogenous damage caused by radiation (UV, X-ray, gamma), hydrolysis, plant toxins, and viruses.

How does UV radiation in sunlight damage DNA?

The longer the exposure to UV light, the more thymine dimers are formed in the DNA and the greater the risk of an incorrect repair or a “missed” dimer. If cellular processes are disrupted because of an incorrect repair or remaining damage, the cell cannot carry out its normal functions.

What can damage DNA?

DNA can be damaged via environmental factors as well. Environmental agents such as UV light, ionizing radiation, and genotoxic chemicals. Replication forks can be stalled due to damaged DNA and double strand breaks are also a form of DNA damage.

What is SOS repair system?

SOS repair refers to the DNA repair system, which uses RecA regulatory protein to inhibit the repressor’s activity and activate the SOS inducer genes to recover the DNA damage. It stands for “Save Our Soul”. The SOS system remains repressed until the conversion of RecA protein into RecA protease.

What enzyme is responsible for proofreading during replication?

Which enzyme is responsible for proofreading during replication? DNA polymerase: DNA polymerase performs proofreading functions during replication using its 3′ to 5′ exonuclease capability.

What changes does UV light produce in DNA molecules quizlet?

Thymine dimers, which can be produced by ultraviolet radiation, can lead to cancer‑causing mutations. C. Exposure to sunlight can create thymine dimers, which prevent the cell from initiating DNA replication.