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aisha2 Forum Newbie Topics: 37 Posts: 411	May 14, 2006 - 3:20 AM       #1 Cloning of a new eukaryotic gene was followed by insertion and ligation of the gene in an expression vector . The protein translated from this gene was then studied on a westren bolt, and probed with 32 P-DNA, yielding a positive result. These findings eliminate which of the following substances as a candidate for the likely gene product? A. CREB B. Protein kinase A C. RNA polymerase D. Sp-1 E. Steroid receptor
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robin082006 Forum Hero Topics: 468 Posts: 5028	May 14, 2006 - 10:43 AM       #2 No idea, maybe E?
doc179 Forum Guru Topics: 67 Posts: 1213	May 14, 2006 - 11:37 AM       #3 B protienkinase A is the ans
aisha2 Forum Newbie Topics: 37 Posts: 411	May 14, 2006 - 1:38 PM       #4 The correct answer is B. The stem suggests that the protein isolated is a DNA-binding protein, since the probing was done with a DNA probe and not an antibody. Protein kinaseA is an enzyme that phosphorylates other proteins rather than interacting with DNA, and therefore would give a negative result with a DNA probe. Protein kinaseA is a cAMP-dependent kinase. CREB (choice A) stands for cAMP response element binding protein. This is a type of DNA-binding protein, which importantly links levels of the second messenger of numerous receptors (glucagon, adenosine, some 5-HT,ADH, TSH, etc.) with expression of critical proteins. RNA polymerase (choice C) is the key enzyme responsible for transcription of DNA into RNA. Transcription is under promoter region control. With in a promoter a critical TATAA sequence is found at -25 and is the essential recognition site for the enzyme RNA polymerase. SP-1 (choice D) is a transcription factor with a zinc finger motif that controls gene Expression in mammalian cells. It is said to function as a "house keeping" factor, allowing other crucial enzymes involved with transcription to operate optimally. Steroid receptors (choice E) also belong to the super family of zinc finger DNA-binding proteins. These characteristic fingers where zinc is bound to a pair of Cys and a pair of His, allow intimate interaction of the protein with major grooves in the DNA molecule. Such interaction is responsible for controlling gene expression and in turn, for assuring a steroid response in the eukaryotic cell. An example would be cortisol and the induction of the enzyme Phosphoenol pyruvate carboxykinase, resulting in increased hepatic gluconeogenesis and therefore hyperglycemia.
leen Forum Elite Topics: 79 Posts: 294	May 17, 2006 - 5:16 PM       #5 can any one pl explain wat is actually said in the q n wat is asked? thanks
Lim Forum Elite Topics: 62 Posts: 210	Jul 28, 2006 - 9:07 PM       #6 this q asks something that does not bind to DNA
rubina Forum Newbie Topics: 2 Posts: 22	Sep 20, 2006 - 3:15 PM       #7 very good aiysha nice explanation
mediocre Forum Elite Topics: 37 Posts: 225	Sep 23, 2006 - 3:50 PM       #8 nice work,aisha..by the way is this from pre-test?

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