The concept underlying the SCGE assay is that undamaged DNA retains a highly organized association with matrix proteins in the nucleus. When damaged, this organization is disrupted. The individual strands of DNA lose their compact structure and relax, expanding out of the cavity into the agarose. When the electric field is applied the DNA, which has an overall negative charge, is drawn towards the positively charged anode. Undamaged DNA strands are too large and do not leave the cavity, whereas the smaller the fragments, the farther they are free to move in a given period of time. Therefore, the amount of DNA that leaves the cavity is a measure of the amount of DNA damage in the cell.
The image analysis measures the overall intensity of the fluorescence for the whole nucleoid and the fluorescence of the migrated DNA and compares the two signals. The stronger the signal from the migrated DNA the more damage there is present. The overall structure resembles a comet (hence "comet assay") with a circular head corresponding to the undamaged DNA that remains in the cavity and a tail of damaged DNA. The brighter and longer the tail, the higher the level of damage.
The comet assay is a versatile technique for detecting damage and with adjustments to the protocol can be used to quantify the presence of a wide variety of DNA altering lesions (damage). The damage usually detected are single strand breaks and double strand breaks. It is sometimes stated that alkaline conditions and complete denaturating of the DNA is necessary to detect single strand breaks. However this is not true, both single- and double strand breaks are also detected in neutral conditions. In alkaline conditions, however, additional DNA structures are detected as DNA damage: AP sites (abasic sites missing either a pyrimidine or purine nucleotide) and sites where excision repair is taking place.
The comet assay is an extremely sensitive DNA damage assay. This sensitivity needs to be handled carefully as it is also vulnerable to physical changes which can affect the reproducibility of results. Essentially, anything that can cause DNA damage or denaturation except the factor(s) being researched is to be avoided. The most common form of the assay is the alkaline version although there is as yet no definitive alkaline assay protocol. Due to its simple and inexpensive setup, it can be used in conditions where more complex assays are not available.
Read more about this topic: Comet Assay
Other articles related to "background":
... Yankee White is an administrative nickname for a background check given in the United States of America for Department of Defense personnel and contractor employees ... Obtaining such clearance requires, in part, a Single Scope Background Investigation (SSBI) which is conducted under the manuals of the U.S ... Individuals having Yankee White clearances undergo extensive background investigation ...
... Depth 9 bit Colors available 512 Colors onscreen Maximum of 482 (241 background, 241 sprite) Palettes Maximum of 32 (16 for background tiles, 16 for sprites) Colors per palette 16 per background palette (color entry ...
... In 1985, a liquormart brought a suit against the liquor control commissioner, arguing, among other things, that the first regulation, which prevented the liquormart from advertising its prices, was unconstitutional ... The Rhode Island Supreme Court, however, held that the regulation did not violate the First Amendment, the Commerce Clause, the Equal Protection Clause, or the Sherman Anti-Trust Act ...
... Well along into his criminal career he was arrested in Scotland and charged with blowing up the safe of the headquarters of the Edinburgh Co-operative Society ... Let out on bail, he fled to Jersey in the Channel Islands where he attempted unsuccessfully to continue his crooked ways ...
... Donny Hathaway - Organ, Electric piano Billy Preston - Organ Sammy Turner - Background Vocals Hubert Laws - Alto Flute Chuck Rainey - Bass J.R ... Bailey - Background Vocals Carolyn Franklin - Background Vocals Erma Franklin - Background Vocals The Memphis Horns - Ensemble The Sweet Inspirations - Background Vocals Jack Adams - Engineer Howard Albert ... Clark - Background Vocals Cornell Dupree - Guitar Jimmy Douglass - Engineer Tom Dowd - Arranger, Producer Chuck Kirkpatrick - Engineer Eric Gale - Bass Lewis Hahn - Engineer Dan Hersch - Remastering Bill ...
Famous quotes containing the word background:
“Pilate with his question What is truth? is gladly trotted out these days as an advocate of Christ, so as to arouse the suspicion that everything known and knowable is an illusion and to erect the cross upon that gruesome background of the impossibility of knowledge.”
—Friedrich Nietzsche (18441900)
“In the true sense ones native land, with its background of tradition, early impressions, reminiscences and other things dear to one, is not enough to make sensitive human beings feel at home.”
—Emma Goldman (18691940)
“They were more than hostile. In the first place, I was a south Georgian and I was looked upon as a fiscal conservative, and the Atlanta newspapers quite erroneously, because they didnt know anything about me or my background here in Plains, decided that I was also a racial conservative.”
—Jimmy Carter (James Earl Carter, Jr.)