1-What is the most common protein structure used to insert into the major groove
ID: 9256 • Letter: 1
Question
1-What is the most common protein structure used to insert into the major groove of the DNA helix?
a. alpha-helix
b. beta-sheet
c. gamma turn
d. zinc atoms
e. loop domain
2-In the function of the lac operon in E. coli, the lac genes are transcribed in the presence of lactose because
a-RNA polymerase binds to the operator
b. the repressor protein binds to the operator.
c. allolactose binds to the repressor.
d. CAP does not bind to the operator.
e. of the absence of cAMP.
3-When tryptophan is present in the environment of E. coli, the tryptophan binds to the
a. trp operon
b. trp promoter
c. trp operator
d. trp repressor
e. trp polymerase
4-Enhancers can function at large distances from promoters because
a. regulatory proteins bind large regions on the DNA
b. the DNA can loop
c. transcription can initiate several kBp upstream of the promoter
d. the signal can be transmitted down the DNA
e. regulatory proteins can initiate transcription
5-Addition of a polyubiquitin chain to a protein
a. targets the protein to the proteasome
b. exports the protein from the nucleus
c. stabilizes the protein
d. increases binding of the protein to DNA
e. opens the chromatin structure
Explanation / Answer
The correct options for the following questions are as follows:
1.
The alpha-helical structure of a protein is formed by the hydrogen bonds that are formed between the N-H group of an amino acid to C=O group of another amino acid.
The aliphatic amino acid leucine has high helix-forming propensity, while Glycine has poor helix-forming propensity. The bulky aromatic amino acids like tyrosine and tryptophan, and branched aromatic amino acid like phenylalanine interrupt the alpha-helical structure. Similarly, the branched aliphatic amino acids like valine and isoleucine also interrupt alpha-helical structure.
Thus, the most common protein structure used to insert into the major groove of the DNA helix is alpha-helix.
Hence, the correct option among the following is (a).
2. The correct option among the following is (b).
3. The correct option among the following is (d).
4. The correct option among the following is (c).
5. The correct option among the following is (a).
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