Biology Paper 2,Nov/Dec 2012  
Questions:   1 2 3 4 5 6 7 8   Main
General Comments

Question 4

()   Explain the application of genetics in marriage counseling giving
       one example                                                                                                 [5 marks]

(b)    A normal male marries a female carrier of haemophilia.  With the
        aid of a genetic diagram, determine what proportion of their offspring
        will suffer from the disease.                                                                        [ 9 marks]

(c)   State the two laws of inheritance propounded by Gregor Mendel.             [ 6 marks]


The question was the most unpopular one among candidates.  Many candidates could not explain the application of genetics in marriage counseling.  Many candidates only mentioned the genotype without mentioning Rhesus.

Many candidates did not take into consideration that  the genetic crossing in the question is a sex linked type of crossing; many used very odd letters for the crossing.

Very few candidates could state the ‘law of segregation and ‘the law of independent assortment’.






Expected answers include:





















4(a)(i)   Application of genetics in Marriage Counselling

             Knowledge of genetics can be used to counsel intending couples to know their blood groups; genotypes; Rhesus factor status; in order to avoid producing children with genetic defects; reduce child mortality e.g. a man with blood genotype AS/SS; should be counselled not to marry a woman with blood genotype
            AS/SS;/ A Rhesus positive man; should not marry a rhesus negative woman/Any other hereditary factor e.g. haemophilia, albinism, diabetes insipidus, cystic fibrosis



(c)   Law of Segregation

       The characteristics of an organism are controlled by a pair of alleles; which segregate/separate during the formation of gametes; so that each gamete contains only one allele.                                                              

       Law of independent assortment

       During the formation of gametes; members of one pair of alleles separate/segregate; independently of the other pair of alleles.

Powered by Sidmach Technologies(Nigeria) Limited .
Copyright © 2011The West African Examinations Council. All rights reserved.