Promoters that are constitutively expressed and needed in all cells (their genes are sometimes called housekeeping genes) have upstream sequence elements that are recognized by ubiquitous activators.

TLS Online TPP Program

#Id: 10468

#Unit 4. Cell Communication and Cell Signaling

Subsequent loss or inactivation of the remaining normal allele in a somatic cell, known as loss of heterozygosity causes cancer to develop.

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#Id: 10469

#Unit 4. Cell Communication and Cell Signaling

Three mechanisms for LOH of tumor-suppressor genes:

Inactivating mutation or deletion

Chromosome missegregation

Mitotic recombination

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#Id: 10470

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 10471

#Unit 4. Cell Communication and Cell Signaling

A mutation, valine to glutamine in the TM region of the HER2 receptor causes dimerization of the receptor, even in the absence of the ligand, transforming it into the oncoprotein NEU, a constitutively active protein tyrosine kinase.

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#Id: 10472

#Unit 4. Cell Communication and Cell Signaling

TLS Online TPP Program

#Id: 10473

#Unit 4. Cell Communication and Cell Signaling

Deletion that causes loss of the extracellular ligand-binding domain in the EGF receptor leads, to

constitutive activation of the kinase activity of the resulting oncoprotein, ErbB.