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تحميل الدليل التدريبي

أسئلة شائعة


   

King Saud University,

College of Science, Biochemistry Department

Final Examination

442 BCH, Molecular Biology-I

 

Name: _____________________

Number: ____________________

 

Q I: _________ /15

Q II: ________ /15

QIII: _________ /15

Q IV: _________ /15

Total Marks: _________ /60

 

Q I: Answer the following as true [ T ] or false [ F ].         1 X 15 = 15 Marks

 

1. Prokaryotic mRNA is usually identical to its primary transcript.   [ T    ]

2. In RNA the number of purines are equal to the number of pyrimidines.  [ F  ]

3. The A and P sites are found on small ribosomal subunit only.    [   F  ]

4. Four nucleotide bases are used to produce a three base codon.   [   T    ]

5. Shine – Dalgarno sequence is the initiation codon in E. coli.   [    F   ]

6. The process of translocation in protein synthesis needs energy which is supplied by GTP.                      [   T   ]

7. Coupled transcription and translation is seen in bacteria.    [    T   ]

8. Trimming of precursor protein is an example of covalent post translational modification.                        [   F   ]

9. Depurination is caused by the hydrolysis of N – β- glycosyl bond between the base and pentose sugar.             [   T   ]

10. Repressor binds to promoter.        [   F   ]

11. Gene amplification is seen in drosophila.             [   T     ]

12. The genetic code is universal.       [   T     ]

13. Meiosis results in the formation of two daughter cells.    [  F      ]

14. The Tm of DNA depends on its AT content.       [   F   ]

15. Histones are seen in prokaryotes.              [   F     ]

Q II: Choose the correct alternative given below each statement.  1 X 15 = 15 Marks

 

  1. The 5’- cap on eukaryotic mRNA functions to

a)      Help in the initiation of translation √

b)      Help the mRNA to come out of the nucleus

c)      Help in folding of RNA

  1. Which of the following has unusual bases

a) mRNA

b) tRNA √

c) rRNA 

  1. Which of the following statement about ribosomes is wrong

a)      They are made up of proteins and mRNA√

b)      Their sizes are expressed as Svedberg ( S ) units

c)      They function in protein synthesis

  1. Anticodon is present on

a)      mRNA

b)      rRNA

c)      tRNA √

  1. In the attachment of amino acid to tRNA

a)      One molecule of ATP is hydrolysed to ADP and PPi

b)      One molecule of ATP is hydrolysed to AMP and PPi √

c)      One molecule of GTP is hydrolysed to GDP and PPi

  1. IF-1, IF-2, IF-3 are

a)      Initiation factors in prokaryotic translation√

b)      Initiation factors in eukaryotic translation

c)      Initiation factors in prokaryotic transcription

  1. During elongation the ribosome

a)      Moves from 5-’ end to 3’- end of mRNA √

b)      Moves from 3’ –end to 5’- end of mRNA

c)      None of the above

  1. Diphtheria toxin

a)      Prevents the release of Ef – Tu

b)      Inhibits peptidyl transferase

c)      Inactivates eEF – 2 √

  1. Addition/deletion of one more base pairs causes

a)      Transition

b)      Transversion

c)      Frame shift mutation √

  1. An example of base analog is

a)      Bromouracil √

b)      Acridine orange

c)      Both the above

  1. DNA sequence where mutations occur frequently are called

a)      Teratogen

b)      Mutational hot spots √

c)      Translocation

  1. Constitutive genes are expressed at

a)      At a constant rate √

b)      At variable rates depending upon the state of the cell

c)      Are also inducible

  1. Isopropyl thiogalactoside is

a)      An analog of lactose

b)      Gratuitous inducer

c)      Both the above √

  1. UV light causes

a)      The formation of thymine dimers √

b)      Causes depurination

c)      Causes alkylation of a base

  1. The codons that code the same amino acid are called as

a)      Degenerate

b)      Synonyms √

c)      Comaless

Q III: Match the following.              1 X 15 = 15 Marks

 

Column A

Column B

Do not code for any protein   (    9 )

1. Polycistronic

Has clover leaf structure    (   15  )

2. Forms the basis for classification of tRNA

The extra arm   (    2   )

3.AUG

Termination codons  (    12  )

4. Complex of mRNA with many ribosomes

Prokaryotic mRNA  (   1   )

5. Papilloma virus

Initiation codon    (    3   )

6.  Operon

RF -1, RF -2, RF -3   (   16  )

7. Helps galactose to enter the cell

Chloramphenicol    (   13   )

8. Seen in collagen

Cancer causing virus   (   5   )

9. Introns

Hydroxylation of proline, lysine  (   8  )

10. Example of carcinogen

Transposons    (   14  )

11. Helps in utilization of galactose

Benzopyrene   (   10  )

12. UAG, UGA, UAA

Cluster of genes having one promoter(  6)

13. Inhibits peptidyl transferase

Β – galactosidase (  11  )

14. Jumping genes

Polysomes     (     4    )

15. tRNA

 

16. Release factors of E. coli

 

17.  mRNA

 

Q IV: Answer all the following.                   5 X 3 = 15 Marks

 

1. Explain the post transcriptional modifications that take in eukaryotic tRNA.  Also name the enzymes catalyzing the reactions.    5 Marks

5’ capping – The cap is 7- methyl guanosine attached backward through a triphosphate linkage to the 5’ end of mRNA catalysed by nuclear enzyme guanylyl transferase.  Methylation is catalysed by cytosolic enzyme guanine – 7-methyl transferase.

Addition of poly – A – tail – catalysed by nuclear enzyme poly-A-polymerase has 40 to 200 adenine nucleotides.

2. Explain what do you understand by ribozyme?     5 Marks

The formation of peptide bond is catalyzed by peptidyl transferase during translation.  The enzyme activity is found in 23 S rRNA found on the 50S ribosomal subunit.  Because rRNA catalyzes this reaction it is called as ribozyme.

 3.  Explain with examples the different types of point mutations.    5 Marks

Silent mutation – The codon containing the changed base codes for same amino acid.  Eg UCA – serine, UCU also serine

Missense mutation – The codon containing the changed base codes for different amino acid.  UCA – serine, CCA – proline,  Sickle cell anemia

Nonsense mutation – The codon containing the changed base becomes termination codon.  UCA – serine, UAA – termination codon 

 

 
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