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Nucleic Acid And Protein Metabolism Question Paper
Nucleic Acid And Protein Metabolism
Course:Bachelor Of Science (Biomedical Science & Technology)
Institution: Kenyatta University question papers
Exam Year:2009
KENYATTA UNIVERSITY
UNIVERSITY EXAMINATIONS 2009/2010
FIRST SEMESTER EXAMINATION FOR THE DEGREE OF
BACHELOR OF SCIENCE IN BIOCHEMISTRY AND BIOTECHNOLOGY
SBC 222: NUCLEIC ACID AND PROTEIN METABOLISM
DATE: Monday 28th December 2009 TIME: 11.00am – 1.00pm
===============================================================================
INSTRUCTIONS: Section A: Answer any two questions (20 marks each)
1.a)Draw a diagram showing the reactions catalyzed by DNA polymerase that
occurs between deoxyribose at the end of the DNA chain and the 5’
phosphate of a deocyribonucleoside triphosphate. Include the chemical
structure of the phosphate group, indicate the location of sugar and base,
and show the rearrangement of electrons that occur. [10marks]
b) DNA synthesis on the lagging strand of E. Coli is a complex process
known to involve proteins. Initiation of a new chain is catalyzed by the
enzyme (i)_______________And elongation is catalyzed by the
enzyme (ii)_____________Synthesis is discontinuous, yielding short
segments called (iii)________________, which are eventually joined by
the enzyme (iv)_____________, which require the cofactor
(v)________________ [10marks]
2. a) Describe the sequence of events in the initiation of transcription by E. Coli
RNA polymerase. [5marks]
b) The specific sequences that E. coli RNA polymerase binds to in E. coli
DNA before initiating transcription generally contain more A=T Base
pairs than G=C base pairs. In no more than a few sentences, speculate, on
why this might be the case. [5marks]
c) Indicate whether each of the following statements is true (T) or False (F).
________________Eukaryotic cells have three distinct RNA polymerases.
________________Eukaryotic mRNA are generally synthesized by RNA
polymerase I
________________Eukaryotic RNA polymerase III synthesizes only
rRNAS.
_____________All tRNAS have the sequence---CCA at their 5’ terminus
____________Eukaryotic RNA polymerases initiate transcription at
specific sites on the DNA (Promoters), but prokaryotic polymerases do
not. [10marks]
3. Using appropriate illustrations, describe DNA repair by the following systems.
a) Base-excision repair. [10marks]
b) Nucleotide excision repair. [10marks]
SECTION B: Answer all questions (10 marks each)
4. Indicate whether each of the following statements is true (T) or false (F).
i) Assembly of a complete ribosome onto a MRNA requires GTP hydrolysis.
ii) Animoacylation or “charging” of tRNA requires the formation of
aminoacyl-AMP intermediate.
iii) Aminoacyl-rRNA binding to the A site of the ribosome requires the
accessory factor EF-Tu and GTU hydrolysis.
iv) Translocation of growing polypeptide from the A and P site on the
ribosome requires EF-G and GTP hydrolysis.
v) Termination of translocation does not require the hydrolysis of any high
energy phosphate bonds.
5. Describe the formation of the initiation complex during protein synthesis in
bacteria.
6.a)List five processing reactions involved in posttranslational modifications.
[5marks]
b) How do the following compounds inhibits protein synthesis? [5marks]
i) Puromycin
ii) Tetracycline.
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