Allelic exclusion Most T cells fully rearrange and express a TCR chain from only one of their two TCR alleles.

TLS Online TPP Program

#Id: 6605

#Unit 7. System Physiology – Animal

Three estrogens are present in the plasma of the human female: 

1β-estradiol

 Estrone

Estriol

TLS Online TPP Program

#Id: 2403

#Unit 3. Fundamental Processes

The cleavage activity is intrinsic to RNA polymerase itself, it is stimulated greatly by accessory factors that are ubiquitous in the three biological kingdoms. There are two such factors in E. coli, GreA and GreB, and eukaryotic RNA polymerase II uses TFIIS for the same purpose. 

TLS Online TPP Program

#Id: 2432

#Unit 3. Fundamental Processes

When the RNA polymerase reaches the termination site, rho first freezes the structure of the polymerase and then invades the exit channel to destabilize the enzyme, causing it to release the RNA.

TLS Online TPP Program

#Id: 3966

#Unit 2. Cellular Organization

In E.coli, Protein HU is a dimer that condenses DNA, possibly wrapping it into a beadlike structure.

TLS Online TPP Program

#Id: 4629

#Unit 13. Methods in Biology

A number of enzymes have been employed for ELISA, including alkaline phosphatase, horseradish peroxidase, and -galactosidase. These assays approach the sensitivity of RIAs and have the advantage of being safer and less costly.