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Biology Paper 2, Nov/Dec 2010  
Questions:   1 2 3 4 5 6 7 8   Main
General Comments
Weakness/Remedies
Strength












Question 4

               (a)            Explain the following terms:
               (i)           test cross;
               (ii)          allele;
               (iii)        albinism;
               (iv)         Sex linkage [8 marks]



(b) A man with normal vision married a woman who is a carrier of colour blindness.
With the aid of genetic diagrams determine the likely status of their offspring. [6 marks]

(c) Outline hamarck's theory of evolution. [6 marks]

 

_____________________________________________________________________________________________________
OBSERVATION

 

This question was the least popular question in this section and many candidates avoided it. Those who attempted it did not do very well, manifesting candidates' aversion for genetics. Some candidates however had very high scores on the question.

Most candidates performed fairly well on the defmition of terms but did not do well in the genetic diagram. They would not correctly express the genotypes of the parents and so this affected the results. .
Some candidates wrote the genotypes of the parents as Tt and IT rather than XBy and XBXb• The
expected answers include:

Parental Phenotype                             Normal                                                         Carrier
                                                                   Male                               X                           Female

Parental genotype                                         XBy                         X                         XBXb

Gametes

                                                                        F1 Genotype

F 1 Phenotype                                                   Normal   normal                    Carrier       colour blind
                                                                             female   male                         female        male                    


Most candidates could properly outline Larmack's theory of evolution but some candidates omitted to state that new characters acquired are passed on to offspring which gives rise to new species.

                            

 

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