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L23 - Gene Variation Genotype-phenotype correlation Dominance,…

- - - - *E.g. Sickle Cell Anaemia:
        Haemoglobin Tetramer of 2 a polypeptide chains & 2 B chains.
        
        4 subunits a =**141 AA each & *B = 146* AA each
        
        In Sickle Cell Anaeamia, single point mutation results in a missense mutation in the protein; Glu => Val in B chain
        
        Pleiotropy
        Most genes have multiple phenotypic effects, aproperty called pleiotropy
        
        This can be seen in human diseases such as
        cystic fibrosis or sickle cell anemia.
        
        In these diseases, multiple symptoms can be
        traced back to one defective allele.
        
        Type of Dominance observed in Sickle Cell Anaemia; depends on phenotypic level of observation
        
        A/A are wild type, RBC never sickle
        
        A/S not anaemic, RBC sickle only under low [O2]
        
        Electrophoresis reveals CODOMIANCE at the molecular level
        
        Physiological responses indicate COMPLETE DOMINANCE at physiological level
        
        Heterozygote has mixture of normal and sickle shaped cells => INCOMPLETE DOMIANCE at the anatomical level
        
        S/S severe anaemia, abnormal Hb & RBC sickle-shaped.
- - - - Phenotype
        
        External genitalia Appear Female, but they don't have functional ovaries.
        
        They neither have proper development of the internal or external genitalia of either sex
  - - - Hormonal Sex (Prenatal Hormones)
        
        Wolffian Duct
        
        Müllerian Duct