Two distinct selection processes are required:

 • Positive selection, which selects for those thymocytes bearing receptors capable of binding self-MHC molecules, resulting in MHC restriction

• Negative selection, which selects against thymocytes bearing high-affinity receptors for self-MHC/peptide complexes, resulting in self-tolerance.

TLS Online TPP Program

#Id: 6021

#Unit 3. Fundamental Processes

Cdc45 and GINS form a stable complex with the Mcm2-7 helicase (called the Cdc45/ Mcm2-7/GINS, or CMG, complex) and dramatically activate Mcm2-7 helicase activity.

TLS Online TPP Program

#Id: 5556

#Unit 7. System Physiology – Animal

Type B intercalated cells have functions opposite to those of type A cells and secrete bicarbonate into the tubular lumen while reabsorbing hydrogen ions in alkalosis

TLS Online TPP Program

#Id: 8057

#Unit 1. Molecules and their Interaction Relevant to Biology

Cysteine, tryptophan, and methionine are not common amino acids: together, they constitute approximately 5 percent of the amino acids in a typical protein. Four amino acids—leucine, serine, lysine, and glutamic acid—are the most abundant amino acids, constituting 32 percent of all the residues in a typical protein.

TLS Online TPP Program

#Id: 8648

#Unit 2. Cellular Organization

During exit from mitosis and G1, 

Cdh1 is de-phosphorylated and APC/Ccdh1 is active.

TLS Online TPP Program

#Id: 9007

#Unit 6. System Physiology – Plant

Forms I, II, and III are catalytically competent, while members of form IV lack Rubisco activity and play other roles in metabolism.