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Biochemistry Of Nucleic Acids Question Paper

Biochemistry Of Nucleic Acids

Course:Bachelor Of Science In Biochemistry

Institution: Egerton University question papers

Exam Year:2005

UNIVERSITY EXAMINATIONS

SECOND SEMESTER 2004/2005

BIOCHEMISTRY OF NUCLEIC ACIDS

TIME:2 Hours

INSTRUCTIONS:

Section A: Attempt All questions-20 Marks

1.Define the following terms.

a) Translation (2 mks)

b) Promoter (2 mks)

c) Operator (2 mks)

2.State whether the following are TRUE or FALSE.The replication of DNA.(6 mks)

a) Occurs by conservative mechanism.

b) Occurs in 3' to 5'direction.

c) Requires the participation of dAmp, Dtmp, Dgmp and Dcmp.

d) Requires the action of DNA ligase.

e) Involves the formation of an RNA primer.

f) Involves DNA Polymerase 1.

3.Which of the following statements concerning transaction in prokaryotes is/are true? (5 mks)

a) The small subunit of ribosome can interact directly with the mRNA.

b)IF-2 binds to the initiator tRNA in a complex containing GDP.

c) There is no requirement for ATP for synthesis of proteins in bacteria.

d) The first amino acid incorporated into all bacterial proteins is a modified form of methionine.

e) EF-G is not required for the synthesis of the first peptide bond of a polypeptide chain.

4.List three ways in which tRNA differs from mRNA and rRNA.(3 mks)

Section B:Attempt any Four questions-50 Marks

5.List the differences in transcription between prokaryotes and eukaryotes.(12.5 mks)

6. A cell-free protein synthesizing system from E coli was depleted of its endogeneous mRNA and then incubated with poly (AG) random co-polymer in which the ration of A to G was 3:1.Predict which amino acids were incorporated into polypeptides and relative frequency of their incorporation.(12.5 mks)

7. a) Parental administration of ricin kills a vertebrate very rapidly.Explain.(12.5 mks)

b) Identify the following types muttions

a) CGA to GGA (2.5 mks)

b) CGA to UGA (2.5 mks)

8. In a chromosome E.coli there are a number of 'hot spots' where mutations occur with higher frequency than elsewhere.Many hot spots are characterized by the presence of the base 5-methycytosine.Why does the presence of this base lead to frequent mutations?(12.5 mks)

9.There are several differences in structure between prokaryotic and eukaryotic mRNAs.Which of them are significant for the mechanisms of translation in the two groups of organisms.(12.5 mks)

Biochemistry Of Nucleic Acids Question Paper

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