IMED2004 Study Guide - Final Guide: Sickle-Cell Disease, Anemia, Hemoglobin
Document Summary
Phenotypes can be observed at several levels: Depends on what level of phenotype is being considered. Haemoglobin tetramer of 2 polypeptide chains & 2 chains. Glu -> val, protein doesn"t fold properly. Phenotypic ratio = 1:2:1, same as genotypic ratio in progeny. As each genotype has its own phenotype: Dominance thus affects the phenotype genes produce, but not the way the genes are inherited. Type of dominance depends on phenotypic level. A/a are wild type, rbc never sickle. A/s not anaemic, rbc sickle only under low [o2] S/s severe anaemia, abnormal hb & rbc sickle-shaped. Negatively charged gln to more neutral val. Hence change in charge so distance travelled is lesser. Not anaemic but if under o2 stress. Incomplete dominance in terms of shape (anatomical) Has some sickly cells when low o2. One trait is dominant, the other trait is recessive.
