Inheritance and Pedigree Charts

Inheritance and Pedigree Charts

1. Co-Dominance

   • both alleles are dominant and expressed equally in the phenotype
   • Example - ABO blood grouping, both alleles A and B are Dominant and so are co-dominant,allele O is recessive

2. Incomplete Dominance

   • One allele is dominant but not completely.
   • the other allele will show in the phenotype, but not to the same extent.
   • Example - Sickle Cell Anemia, HH (normal), HsHs (sickle-cell anemia), HHs (sickle cell trait - 30%)

3. Sex - Linkage

   • Genes attached to X chromosome are sex linked genes as Y chromosome carries almost no genes.
   • Conditions will likely show in the phenotype of males
   • Examples - Red/Green colour blindness, Haemophilia, Muscular Dystrophy.

4. Pedigree Charts

   • Autosomal Dominant Inheritance.
     • *Parents who are unaffected have unaffected children. * the characteristic is seen in every generation. *Both sexes are equally affected.
   • Autosomal Recessive Inheritance
     • *Parents who are both heterozygous can have affected children. *Children of affected parents always inherit the recessive allele. *both sexes are equally affected. * can skip generations
   • Sex - linked Inheritance
     • *Many more males then females are affected. *only female can be carriers. *can skip generations.

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