WAEC/ WASSCE/ NOVDEC Past Questions and Answers on Nucleic Acids and Protein Synthesis

 SSCE/WASSCE/GCE PAST QUESTIONS AND ANSWERS

OBJECTIVE

1.      The DNA molecule is a chain of repeating

A. nucleosides           

B. nitrogenous bases   

C. sugar phosphates  

D. nucleotides

2.      The biological factor that is unique to each individual is the

A. DNA                     

B. eye colour      

C. blood group       

D. RNA

3.      If a DNA strand has a base sequence TCA, its complementary strand must be

A. ATG      

B. TAG     

C. GAT     

D. AGT

4.      Paternity dispute can most accurately be resolved through the use of

A. Finger printing            

B. blood group typing  

C. DNA analysis   

D. tongue-rolling

5.      An accurate identification of a rapist can be carried out by conducting a

A. RNA analysis      

B. DNA analysis      

C. blood group text  

D. behavioral traits test

Use the diagram below to answer question 6 & 7

6. The diagram represents structure of

A. proteins                   

B. chromosomes     

C. RNA    

D. DNA

7. The part labelled I represents the

A. base pairs             

B. ribose sugar   

C. phosphate linkage      

D. deoxyribose sugar

8. Which of the following is not a constituent of DNA?

A. Purine                   

B. Uracil               

C. Cystocine    

D. Deoxyribose

9. Protein formation is associated with 

A. ribosome              

B. mitochondrion      

C. golgi bodies   

D. lysosomes  

10. During protein synthesis, an anticodon of transfer RNA (tRNA) pairs with 

A. amino acids in the polypeptide

B. DNA nucleotides bases 

C. ribosomal RNA (rRNA) nucleotide bases

D. messenger RNA (mRNA) nucleotide bases

11. In the formation of a mRNA molecules, thymine is replaced by 

A. Adenine              

B. Cytosine         

C. Guanine       

D. Uracil

12. The pyrimidine bases found in DNA are

A. adenine and guanine 

B. adenine and cytosine 

C. cytosine and guanine 

D. cytosine and thymine 

13. The sequence of amino acids in a develop protein chain in a cell is determined by 

A. mRNA               

B. ribosome         

C. RNC-polymerase        

D. tRNA 

14. Protein synthesis occurs 

A. in the mitochondrion

B. in the golgi body

C. on the ribosome 

D. on the endoplasmic reticulum

15. In protein synthesis, the anticodon of tRNA pairs with a complementary codon on the molecule of 

A. DNA   

B. mRNA   

C. RNA   

D. rRNA

16. DNA molecules always have 

A. equal number of phosphate groups, purines and pyrimidines 

B. equal number of ribose sugars, purine and pyrimidines 

C. equal number of purine and pyrimidines

D. fixed number of number nucleotides and nucleosides 

Consider the following steps in protein synthesis and use them to answer questions 17 & 18

I. Attachment of mRNA to ribosome

II. Formation of peptide bond 

III. Collection of amino acids by tRNA 

IV. Formation of mRNA

17. The correct sequence of events during protein synthesis is 

A. I, II, III and IV      

B. III, I, IV and II      

C. IV, I, III and II    

D. IV, III, II and I

18. Which of the steps constitutes transcription of genetic code? 

A. I          

B. II           

C. III          

D. IV 

19. Which of the following is not a correct base pairing on the DNA strands? 

A. Adenine, Thymine  

B. Cytosine, Guanine

C. Guanine, Cytosine 

D. Uracil, Thymine 

20. The organic molecule(s) present in the nucleus is/are 

A. DNA                   

B. protein, DNA and RNA        

C. RNA and ATP

D. RNA

Answers

1. B	6. D	11. D	16. C
2. A	7. A	12. D	17. C
3. D	8. B	13. A	18. D
4. C	9. A	14. C	19. D
5. B	10. D	15. B	20. B

THEORY

1. (SSCE 1995, Q1) (a) Describe how protein is being synthesized in animal cell. 

Solution 

Protein synthesis occurs on the ribosomes in the cytoplasm. The two strands of DNA in the nucleus separate, with one of the strands having coded information of the DNA copied across into mRNA strand. The mRNA is released and moves into the cytoplasm through the nuclear membrane. This mRNA bears a series of specific base sequence which are instructions for protein synthesis. The mRNA with its base sequence being specific for one amino acid is attached to a ribosome in the cytoplasm. In the cytoplasm of every cell are millions of free amino acids. Each tRNA molecule contains a sequence of three bases which code for specific amino acid. The tRNA molecules moves around in the cytoplasm, picking up free amino acids and transferring them to mRNA on the ribosome. Its three bases (anticodon) join up with corresponding bases (codon) on the mRNA molecule according to the pairing rule: A-G and G-C. At the same times, its amino acid links up with an amino acid already in position on the mRNA by a peptide link. This process continues, building up a chain of amino acid i.e. a polypeptides chain. This is released from the mRNA into the cytoplasm and joins up with other polypeptide chains, eventually forming a protein in molecule. 

2. (SSCE 1997, Q1) (a) (i) What is RNA?

(ii) Discuss the role of RNA in protein synthesis.

Solution 

(i) RNA is made up of a long strand of nucleic acids found in nucleus and cytoplasm of a cell. It consists of small subunits called nucleotides. It is singled stranded and there are three types i.e. mRNA, tRNA, and rRNA. 

(ii)  The synthesized mRNA molecule leaves the nucleus and enters the cytoplasm, where it directs the synthesis of the protein. It bears a series of specific sequences or nucleotides which are the instructions for the protein synthesis. Each tRNA molecule contains a sequence of three bases which code for specific amino acid and enable it to become attached to definite part of mRNA. The tRNA carries specific amino acid in the cytoplasm to mRNA on the ribosome. Adjacent amino acids are linked together by peptide bonds. tRNA adds more amino acids by moving along the ribosome. 

3. (SSCE, 2004 Q6) (a) Name the main components of DNA molecule. 

(b) Describe the role of DNA in protein synthesis. 

Solution 

(a) Main components of DNA

o Deoxyribose sugar 

o Phosphate 

o Nitrogen base

(b) Role of DNA in protein synthesis 

DNA is in the nucleus. During protein synthesis the molecule unwinds and one of the strands acts as a temperate, from which mRNA strands is formed or transcribed. The mRNA is released and moves out of the nucleus into the cytoplasm and attaches itself to the ribosome and sequence is read by the tRNA. 

4. (WASSCE, 2011 Q6) (a) What is RNA? 

(ii) Outline the role of RNA in protein synthesis. 

Solution 

Refer to blog content 

5. (WASSCE, 2013 Q4) (c)(i) Describe the structure of DNA. 

(v) State three structural difference between DNA and RNA.

Solution 

Structure of DNA

 DNA consists of nucleotides. Each nucleotide consists of three different molecules which are nitrogenous base, desoxyribose sugar and phosphate.

 The nitrogenous bases are purine and pyrimidine

 The purine molecule is made up of adenine and guanine. 

 Pyrimidine molecule is made of cytosine and thymine. 

 The deoxyribose sugar combines with the phosphate to form the back-bone of DNA. 

 DNA consists of two chains twisted to form double-helix structure. The strands are held together by hydrogen bonds between the bases; adenine pairs only with thymine while guanine pairs only with cytosine. 

(ii). Structural difference between RNA & DNA

RNA	DNA
Single stranded	Double stranded
Uracil is present	Thymine is present
Ribose sugar present	Deoxyribose sugar present
Three form of RNA present (mRNA/tRNA RNA)	Only one form of DNA present

 

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