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 Q1  



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Author8 Posts
  #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





  #2

No idea, maybe E?


  #3

B protienkinase A is the ans


  #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.



  #5

can any one pl explain wat is actually said in the q n wat is asked?

thanks



  #6

this q asks something that does not bind to DNA





  #7

very good aiysha nice explanation


  #8

nice work,aisha..by the way is this from pre-test?





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