1. GENETIC CONCEPTS:
   • *Monohybrid cross /monohybridism= when a single factor is involved in cross breeding. Eg Tallness x shortness
   • *Dihybrid cross /dihybridism = when two factors are involved in cross breeding. eg Tall &Light x short & dark
   • *Phenotype ======= physical/outward appearance of an organism
   • *Genotype ======= genetic composition of an organism
   • *Alleles ======= alternate forms of genes/pairs of
                                 Genes (TT, Tt, tt, WW, Ww, ww)
   • *Homozygous alleles== similar/identical pairs of
                                            Genes (TT, tt ,WW, ww, BB, bb)
   • *Heterozygous alleles== dissimilar pairs of genes(Tt, Ww, Bb Zz, Ll, Dd)
   • *Prepotency======= ability of an organism/individual to transmit its characteristics to the offspring/progeny.
   • *Atavism======== Reappearance of ancestral characteristics
2. MONOHYBRID CROSS
   -when a single factor is involved in cross breeding
   1. WITH DOMINANCE (COMPLETE DOMINANCE)
      T=tall, t=short
      
      Pure bred (very) tall===
      Hybrid (medium) tall==
      Reccessive (very) short
   2. WITHOUT DOMINANCE (INCOMPLETE DOMINANCE)
      *Mendell used flowers of different colours
      eg Red flowers(R) and a White flower(r)
      
      For you to do:
      Give the ratio of each of the following:
      Phenotype=
      Genotype=
      Give the % of :
      Red flowers=
      Pink flowers=
      White flowers=
3. CO-DOMINANCE
   • There is NO Recessiveness
   • Both characteristics (colours) are dominant
   • Both colours of the parents will equally appear in the offspring
   • The offspring will have a Roan colour
     
     SUMMARY
     

     	DOMINANCE	INCOMPLETE DOMINANCE	CO-DOMINANCE
     COLOUR OF OFFSPRING	* One colour is dominant and the other is recessive. *The offspring resembles one of the parents	* There is no dominance * None of the parents’ colours will be visible to the offspring * The offspring has one colour which is completely different from its parents	* There is no recessiveness * Both colours are dominant * Both colours of the parents equally appear in the offspring * This colour of the offspring is called a Roan colour (White and Black spots/patches)

4. DIHYBRID CROSS
   -Two factors are involved in cross breeding
   Mendell used seeds
   
   Punette Square- F1
   

   RY	ry	ry	ry	Ry
   RY	RrYy	RrYy	RrYy	RrYy
   RY	RrYy	RrYy	RrYy	RrYy
   RY	RrYy	RrYy	RrYy	RrYy
   RY	RrYy	RrYy	RrYy	RrYy

    
   Punette Square
   

   RY	Ry	rY	ry
   RY
   Ry
   rY
   Ry

   RATIO: Phenotype:
   
   Round &Yellow
   Round & green
   wrinkled & Yellow=
   wrinkled & green=
   MENDELL’S LAWS OF INHERITANCE
   • First Law : When Mendell discovered GENES
     - Genes are transmitted from one generation to the next.
   • Second Law : Dominance and Recessiveness
     -Some genes are dominant and others are recessive
   • Third Law : Law of Segregation
     - During meiosis pairs separate to form gametes
     eg: 
     
   • Fourth Law: Independent assortment /Dihybrid cross /Dihybridism
     -Independent pairs of genes are released during meiosis
     eg: 
     

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