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Biology Paper 2,May/June 2008.  
Questions: 1 2 3 4 5 6 7 8 Main
General Comments

Question 4

(a)        Describe the main stages of mitotic division.                                 [16 marks]
(b)        State four ways in which mitosis is important to living organisms. [4 marks]



This was the least popular question in this section and those candidates who attempted it generally performed poorly.  Many of the candidates merely stated the main stages of mitotic division and could not describe the processes. Even in stating the stages many candidates lost marks due to spelling errors.  A good number of candidates who went ahead to describe the stages mixed up the processes involved in the different stages.  The expected answers are as follows:

Main Stages of Mitotic Division
Prophase -  Chromosomes appear as two threads/chromatids; chromatids are long thin and/later become shorter and thicker; and joined together at the centromere; the nuclear membrane; and the nucleolus disappear; spindle fibres form in the cytoplasm; with a pair of centrioles; one at each pole.

Metaphase – Spindle formation is completed; the chromosomes are arranged at the equator of the spindle; attached by their centromeres; centromeres divide; and begin to move apart;

Anaphase – The paired chromatids are pulled apart/separated; migrate/move towards opposite poles; spindle fibres shorten; chromatids reach the poles;

Telophase - Fibres disappear; nuclear materials and nucleous are formed; bounded by nuclear membrane; the cell constricts; to form two daughter cells.

Most candidates who attempted 4(b) could only state two importance of mitosis. The answers include:

Importance of mitosis                                                                                                                                                                     Promotes cell growth; replacement/repair of damaged tissues; basis of a sexual/vegetative reproduction; produces genetically identical offspring; which are identical to the parents; maintains the diploid number of the chromosome of the cell.

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