The growth factor SC stimulates the proliferation of cultured chicken cells. The
ID: 67550 • Letter: T
Question
The growth factor SC stimulates the proliferation of cultured chicken cells. The receptor the binds SC is a receptor tyrosine kinase (RTK), and many chicken tumor cell lines have mutations in the gene that encodes this receptor. Which of the following types of mutation would be expected to promote uncontrolled cell proliferation? a mutation that destroys the kinase activity of the receptor a mutation that prevents the binding of the normal extracellular signal to the receptor a mutation that inactivates the protein tyrosine phosphatase that normally removes the phosphates from tyrosines on the activated receptor a mutation that prevents dimeri/ation of the receptorExplanation / Answer
Option (c) is the correct answer.
Receptor tyrosine kinases (RTKs) are the receptors present on the cell surface which can bind to specific growth factors. When the growth factor attaches to the receptor, the dimerization of the receptor with the neighbouring receptor tyrosine kinase is stimulated. This activates the kinase or phosphorylation activity of the receptor. The receptor phosphorylates its own tyrosine residues and this begins a signal transduction pathway inside the cell.
The receptor tyrosine kinases have been found to play an important role in control of cell division, differentiation, and so on.
The uncontrolled activation of these receptors has also been shown to lead to uncontrolled cell division and cancer.
In normal cells, the activity of these receptors is kept in check by enzymes called protein tyrosine phosphatases. These enzymes remove the phosphate groups from the tyrosine residues of proteins. This dephosphorylation can lead to inactivation of that protein. Thus, the activity of protein tyrosine phosphatases is necessary for controlled and optimal activity of the receptor tyrosine kinases.
Therefore, mutations that inhibit the activity of protein tyrosine phosphatases have been shown to remove the check over receptor tyrosine kinases leading to uncontrolled cell division.
The other options indicating mutations destroying kinase activity of receptor, preventing binding of signal to receptor or preventing dimerization of receptor will inhibit the activity of the receptor tyrosine kinase and in fact check cell proliferation.
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