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: 953

#Unit 5. Developmental Biology

In Strongylocentrotus purpuratus, the acrosome reaction is initiated by a repeating polymer of fucose sulfate.

TLS Online TPP Program

#Id: 3220

#Unit 4. Cell Communication and Cell Signaling

Direct-acting carcinogens

Highly reactive compounds that can react with and modify nucleotide bases in DNA so as to distort the normal pattern of base pairing

TLS Online TPP Program

#Id: 8946

#Unit 2. Cellular Organization

An inhibitor of the GTPase, called Kin4, localizes to the parent cell but is absent from the bud.

TLS Online TPP Program

#Id: 6366

#Unit 2. Cellular Organization

TLS Online TPP Program

#Id: 3514

#Unit 2. Cellular Organization

Overlapping gene are the same sequence of DNA encodes two nonhomologous proteins because it uses more than one reading frame.