The K+ that enters hair cells via the mechanically-sensitive cation channels is recycled. In the cochlea, K+ eventually reaches the stria vascularis and is secreted back into the endolymph, completing the cycle

TLS Online TPP Program

#Id: 10474

#Unit 4. Cell Communication and Cell Signaling

A point mutation substitutes any other amino acid

for the glycine12 in the Ras, the normal protein is converted into a constitutively active oncoprotein

TLS Online TPP Program

#Id: 10475

#Unit 4. Cell Communication and Cell Signaling

Ras-GAP protein, 

NF1 (neurofibromatosis)

TLS Online TPP Program

#Id: 10476

#Unit 4. Cell Communication and Cell Signaling

Inherited a single mutant NF1 allele then develop neurofibromas, a benign tumor of the sheath cells that surround nerves, caused by loss of both alleles through LOH.

TLS Online TPP Program

#Id: 10477

#Unit 4. Cell Communication and Cell Signaling

In certain tumors of antibody-producing B lymphocytes, the cyclin D1 gene is translocated & its transcription is

under the control of an antibody-gene enhancer, causing elevated cyclin D1 production.

TLS Online TPP Program

#Id: 10478

#Unit 4. Cell Communication and Cell Signaling

Loss of p16 mimics overproduction of cyclin Ds

TLS Online TPP Program

#Id: 10479

#Unit 4. Cell Communication and Cell Signaling

Loss-of-function mutations in PTC1 permit cell

proliferation in the absence of an Hh signal