Operation of the C4 cycle requires the cooperative effort of both cell types. No mesophyll cell of a C4 plant is more than two or three cells away from the nearest bundle sheath cell.

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.

TLS Online TPP Program

#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

TLS Online TPP Program

#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.

TLS Online TPP Program

#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.