nbme 4 - poojy36

[ArchivalUser]

1) a synthetic glycoprotein similar to G-CSF is designed .which of teh foll is a characteristic of G-CSF activity that must be taken into account to assure similar biological function?

a) activation of specific cell surface receptor
b0 display of cross - species functionality
c) down regulation of cell growth
d) production by endothelial cells
e( stimulation of megakaryocyte cell production

2)Sum oncogenes are mutanta of normal cell surface receptors that hv tyrosin ekinase activity in their cytoplasmic domains .this type of mutation of such a receptor that is most likely to result in cell transformation in a mutanat protein with which of the foll charac?

a) constitutive activation of cellular trans cription
b) deletion of the cytoplasmic domain
c) failure to become phosphorylated upon receving signal
d) failure to receive the signal that normally activates cell trans cription
e) recognition of different signal than usual

[ArchivalUser]

not sure guess

1-c;2-e

[ArchivalUser]

1.a
2.a

[ArchivalUser]

1-a
2-d

[ArchivalUser]

1.a
2.a.

I don't think D is correct. A is most common case for receptor kinase mutations in tumor formation. A typical example is t(9;22) translocation in CML.

[ArchivalUser]

sage actually poojy has wroted it so ambigious that i thought it was somthing abt tyrosine kinase and dephosphorylation

[ArchivalUser]

Sorry, abl kinase is not receptor tyrosine kinase, but over activated after fusion with bcr. Her2 mutation is a case of RTK mutation.

appendicitis, RTK mutation causes constitutive activation of signal pathway, which do not ligand activation any more, is very common in tumorogenesis. Failure to receive signal usually cause cell death, rather than cell over growth. Disregulation of dephospharylation is also one of mechanisms of tumor formation. but in this Q, dephospharylation is not involved.