Consider the following diagram showing the working of the lac operon in E.coli in the presence of an inducer and choose the correct statement from the ones given below:
  

1.	A is the inducer and can be either lactose or cAMP.
2.	B is the enzyme that will metabolize glucose, the preferred energy source.
3.	Some amount of C will be present in the cell even if lactose is absent.
4.	The absence of D will stop lactose from entering the cell.

Study the diagram given below and choose the correct information that can be deduced:
   

Consider the transcription unit given in the following diagram and choose the correct statements:
  

Which of the following cannot be inferred from the information given in the following diagram?
 

Match each item in Column I with one item in Column II and chose your answer from the codes given below:
Column I                            Column II
(anibiotic)                          (effect)
I. Tetracycline                     1. inhibits binding of amino acyl tRNA to ribosome
II. Streptomycin                 2. inhibits initiation of translation
III. Chloramphenicol           3. inhibits peptidyl transferase
IV. Erythromycin                 4. inhbits transloaction of mRNA along ribosome
Codes:
     I    II    III    IV
A.  1    2     3     4
B.  2    1     4     3 
C.  2    1     3     4
D.  1    2     4     3

Match each item in Column I with one item in Column II and chose your answer from the codes given below:
Column I                        Column II
(mRNA codons)             (Amino acid)
I. GUG                          1. Tryptophan
II. UGG                         2. Valine
III. UAC                        3. Glutamic acid
IV. GAG                         4. Tyrosine
Codes:
I II III IV
A. 1 2 3 4
B. 2 1 4 3
C. 2 1 3 4
D. 1 2 4 3

Which of the following was presented as evidence in favor of “the RNA world” hypothesis?

1. The fact that DNA can encode genetic information

2. The fact that enzymes, made of protein, can catalyze biological reactions

3. The discovery that some enzymes are composed of RNA rather than protein

4. The discovery of new life forms that encode their genetic information in RNA rather than DNA

The wobble effect is the:

1. Lack of precision with regard to the third base in the codon and anticodon
2. Instability of the DNA molecule when unwound
3. Instability of pairing when a purine pairs with another purine
4. Undulating movements of mRNA

An operon is a:

1. Protein that suppresses gene expression
2. Protein that accelerates gene expression
3. Genes that switch other genes on or off
4. Cluster of structural genes with related functions

The activity of a repressor depends on whether:

1. The repressor is positioned next to the operon
2. The repressor is positioned next to the promoter
3. A key substance in the metabolic pathway is present
4. There is enough RNA polymerase present