Telomeres cluster on the nuclear envelope just prior to homologous chromosome synapsis during meiosis.

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#Id: 7224

#Unit 5. Developmental Biology

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.

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#Id: 6876

#Unit 3. Fundamental Processes

Most Polycomb proteins are subunits of one of two classes of multiprotein Polycomb repressive complexes: PRC1 and PRC2.

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#Id: 5704

#Unit 7. System Physiology – Animal

ACTH (corticotropin) 

controls the secretion of cortisol by the activation of adenylyl cyclase via Galpha s.

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#Id: 8404

#Unit 2. Cellular Organization

The increase in Ca2+ concentration is transient because the Ca2+ is rapidly pumped back into the SR by an abundant, Ca2+ ATPase.

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#Id: 9464

#Unit 4. Cell Communication and Cell Signaling

The SH2 domain binds strongly to short target peptides containing a critical four-residue core sequence:: 

phosphotyrosine–glutamic acid–glutamic acid–isoleucine