1. (a)   (i)   What is a gene?                                                                                                 [2 marks ]
          (ii)    Differentiate between the terms genotype and phenotype                               [2 marks ]
   (b)    Explain the following terms:
           (i)   hybrid;
          (ii)    pure breeding;
         (iii)     nucleotide.                                                                                                       [6 marks ]
   (c)    In garden pea seeds, smooth seed coat is dominant over rough seed coat. 
           With the aid of  a genetic diagram, determine the result expected if a
           homozygous rough pea is crossed with a smooth seed coat plant whose parent
           were rough coated.                                                                                                 [10 marks]

 

observation

    Most candidates gave the definition of a gene as the basic unit of inheritance located on the
   chromosome, which can be transferred from parents to offspring.  Most candidates also could
    properly state the difference between genotypes and phenotypes.
The candidates could not properly define the meaning of pure breeding and nucleotide.  Candidates gave wrong definition of pure breeding as a process of producing a particular genotype.  Nucleotide was given as a component of DNA.
    Most candidates forgot to represent the gene for smooth coat as ‘S’, and gene for rough coat 
    as ‘s’, and so lost few marks.
    They also performed poorly in the genetic crossing, expected answers  include:
    Pure- Breeding
   A process of producing a particular genotype; over many generations.
   Nucleotide
   The basic building block of a nucleic acid; consisting of a ribose/deoxyribose/pentose, a
   phosphate group and a nitrogen base.
   Crossing for garden peas
               S  =   Gene for smooth coat
               s   =   Gene for rough coat
   Parents:
               Phenotype:  Homozygous rough x smooth whose parent was rough

         
              Phenotype:    ½ Rough, ½ smooth