Model STPM Biology Exam Question

Model STPM Biology Exam Questions

Question 1

i) What is the agent that acts on both the plasmid and DNA fragment before the cloning process. Give one example. [2M]

ii) The cleaved plasmid and DNA fragment is incubated with a biochemical agent before transformation can be done. What is the agent and what is its function? [2M]

iii) Define transformation. [2M]

iv) Name a host cell which is normally used in the transformation process and explain how the DNA inserted into the plasmid can be cloned in the named host cell? [3M]

v) State TWO reasons why the cell you have named in (iv) is suitable as a host cell. [2M]

vi) Describe a method to screen the transformant. [3M]

vii) What is the aim of cloning DNA within a host cell? [3M]

Question 2

The diagram above shows a model of an operon in a prokaryotic cell.

a) Name the processes X, Y and the P compound. [3M]

b) Mark with (*) the position of promotor in the diagram. [1M]

c) Define an operon. Mark the position of the operon in the diagram. [2M]

d) Given that the operon above is a lac operon,
(i) Is it an inducible or repressible operon? Explain your answer. [2M]
(ii) Name two examples of P compound and state their functions. [4M]
(iii) When will the operon start to operate and explain how does it operates. [3M]
(iv) Is the operon an anabolic or catabolic operon? Explain your answer. [2M]

e) If the operon above is a trp operon,
(i) What is the function of tryptophan? [1M]
(ii) Explain the function of trp operon. [2M]

f) What is the function of the following components?
(i) regulator gene [1M]
(ii) promoter gene [1M]

Question 3 (Essay)

a) Compare TWO genetic screening procedures which are used on a pregnant lady.

b) Down Syndrome and Cri du Chat Syndrome are both effects of chromosomal mutations. Compare the diseases.

c) Using an example, discuss how allopolyploidy can occur in plants.

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