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Biology Paper 2, May/jun 2014  
Questions:   1 2 3 4 5 6   Main
General Comments
Weakness/Remedies
Strength












Question 4

A survey to determine blood groups was carried out on 250 people living a community.     
The results are represented in the Table below.

Blood group

Percentage

A

8.0

B

14.0

AB

32.8

O

45.2

(a)        (i)         Explain the term co-dominance .       [2 marks]
            (ii)        Calculate the number of individuals with co-dominant blood group.     [3 marks]
            (iii)       What is the total number of individuals in the Table that are able
                        to donate blood to an accident victim with blood group B?      [6 marks]

(b)        A man whose blood group is heterozygous A is married to a woman whose
            blood group is AB.  With the aid of a genetic diagram, suggest the possible
            blood groups of their children.       [9 marks]

_____________________________________________________________________________________________________
OBSERVATION

This was the most unpopular question among the candidates.  The few candidates that
attempted it did so poorly.

The expected answers are:
                         
     (a)(i)  Codominance
         Codominance occurs when both the alleles in an heterozygous individual are fully
         expressed; that is both alleles exert their effects so that the hybrid has a phenotype;
         that is different from what the parents exhibit.

             (ii)   Calculation of Individuals with Co dominant blood group
Mention of codominant blood group is AB                                                             

Evidence of Calculation

32 .8% of 250                                                                                                           
                  OR                                                                                                                               
          32.8   x 250
          100                                  
                                                =   82 individuals/people                                                     

(iii)   Total number of individuals that can donate blood  to blood group B
   The total number of individuals will be from groups B and O                                           

  • 14% of the population is Blood group  B

14% of 250                                                                                                                
         OR                                                                                                                    
14   x 250             
100
                                 =   35 individuals/people                                                                       

  • 45.2% of the population is blood group O

45.2% of 250                                                                                                             

45.2  x 250               =   113 individuals/people                                                         
100

 

 

  • Total number of people          =   113 of group O

                                                                   35 of group B
                                                                 148 individuals/people can donate blood to the
                                                                        accident victim in B                                                                                                                 
                        OR

The Total number of individuals from (B and O) blood group B and O                  
                                                                                                                                                           

  • 14% + 45.2%  =  59.2%                                                                                              
  • 59.2% of 250                                                                                                               

 

  •                                                                                                                          

=          148 people/individuals                                                           

      (b)     Crossing
 
                                                                                                                                                                                                      

                                OR
Punnet Square – scoring/ (Punnet Square)


                       

 

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