Topoisomerase
A class of enzymes that alter the supercoiling of double-stranded DNA. (In supercoiling the DNA molecule coils up like a telephone cord, which shortens the molecule.) The topoisomerases act by transiently cutting one or both strands of the DNA. Topoisomerase type I cuts one strand whereas topoisomerase type II cuts both strands of the DNA to relax the coil and extend the DNA molecule.
The regulation of DNA supercoiling is essential to DNA transcription and replication, when the DNA helix must unwind to permit the proper function of the enzymatic machinery involved in these processes. Topoisomerases serve to maintain both the transcription and replication of DNA.
Aside from topoisomerases I and II, there are more discovered topoisomerases. Topoisomerase III may regulate recombination while topoisomerase IV regulates the process of segregating newly replicated chromosomes from one another.
Read Also:
- TORCH screen
A blood test that is designed to screen for a group of infectious agents known by the acronym TORCH, which stands for Toxoplasma gondii, other viruses (HIV, measles, and so on), rubella (German measles), cytomegalovirus, and herpes simplex. All these infectious agents are teratogens (agents that are capable of causing birth defects). The TORCH infectious […]
- Tornado supplies kit
small canister, ABC type Tube tent Pliers Tape Compass Matches in a waterproof container Aluminum foil Plastic storage containers Signal flare Paper, pencil Needles, thread Medicine dropper Shut-off wrench, to turn off household gas and water Whistle Plastic sheeting Map of the area (for locating shelters) 1 2 Next
- Thyroid hormones
Chemical substances made by the thyroid gland, which is located in the front of the neck. This gland uses iodine to make thyroid hormones, which are essential for the function of every cell in the body. They help regulate growth and the rate of chemical reactions (metabolism), and are involved in the circadian rhythms that […]
- Thyroid hormone receptor
A molecule that receives a thyroid hormone and permits it to dock on the nuclear membrane of a cell. The thyroid hormone receptors (THRs) belong to a family of nuclear receptors that function as hormone-activated transcription factors and act by modulating the expression of genes. THRs bind DNA in the absence of hormone, usually suppressing […]
- Torsion fracture
A fracture, also called a spiral fracture, in which a bone has been twisted apart.