You accidentally exposed your cell culture dish to radiation, but you are not sure of the precise wavelength of the exposure
How can you use the induced DNA damage to tell whether the radiation was UV or higher energy? What is the difference between the DNA damage caused by UV radiation compared to higher-energy radiation? Which type of damage is likely to be the most lethal to your cells?
Any radiation energy in wavelengths shorter than 380 nm is mutagenic. Ultraviolet radiation is a commonly encountered mutagen that creates pyrimidine dimers in DNA, and these can lead to base-pair substitution mutations. If the dimer cannot be removed, it may also lead to replication stalling at the site of the lesion. Replication blockage by pyrimidine dimers may induce reinitiation of DNA synthesis at an adjacent RNA primer site. This reinitiation of replication potentially leaves gaps spanning dozens to hundreds of nucleotides in newly synthesized DNA strands, but the gaps are subsequently filled by translesion DNA synthesis, which is carried out by specialized bypass DNA polymerases that can replicate across the gaps but lack proofreading capabilities.
Higher-energy radiation can induce DNA strand breaks. DNA can be damaged in multiple ways, the most serious being the induction of DNA single-strand or double-strand breaks. These breaks potentially block DNA replication and thus pose a significant threat to the integrity and survival of affected cells. DNA damage of this type is dealt with by specialized strand-break repair mechanisms. Double-strand DNA breaks are often the most difficult to repair and thus are the most lethal to cells.
You might also like to view...
Ammonia-oxidizing bacteria play an essential role in the nitrogen cycle by ____
a. converting ammonia into nitrogen oxides b. converting ammonia into nitrites c. converting ammonia into ammonium d. converting nitrites into ammonia e. converting nitrites into nitrogen oxides
Which gland is both an exocrine and endocrine gland?
a. pancreas b. adrenal c. ovary d. thyroid e. pituitary
____ is the predominant photosynthetic product carried in phloem
a. Glucose b. Cellulose c. Sucrose d. Maltose e. Fructose
The common basilisk lizard will run across water on its hind legs in an erect position when startled by predators. This lizard has large feet and flaps of skin along its toes. What properties of water allow this lizard to walk on water?
A. Hydrogen bonds hold water molecules together; many hydrogen bonds must be broken for water to evaporate. B. The surface tension created by hydrogen bonds is greater than the weight of the lizard initially. C. Polar molecules are attracted to ions and polar compounds, making these compounds soluble. D. Hydrogen bonds absorb heat when they break and release heat when they form. This helps to minimize temperature changes.