bicd 100 - lecture 12

bicd 100 - lecture 12 - LECTURE - 12 Codominance, Blood...

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Unformatted text preview: LECTURE - 12 Codominance, Blood Groups Multiple alleles (allelic series) • More than 2 alleles in a population. • Only two alleles in any individual. • Inheritance similar to when 2 alleles are present but greater variety of genotypes and phenotypes. • Example: ABO blood group system Three alleles IA, IB and i (simplify to A, B, O) The ABO system 6 Genotypes AA AO 4 Phenotypes (blood types) A A BB BO B B AB OO AB O IgM: Earliest antibodies expressed in fetus (20 weeks) Do not cross placenta Mystery! Charlie Chaplin and Joan Barry (1941) Joan: Blood type A Child: Blood Type B Chaplin: Blood type O “It is impossible to say whether the two were still having intercourse late enough to conceive the child which was born on Oct. 3, 1943. Chaplin claimed they had gone their separate ways more than a year before. Joan insisted otherwise. She related a tantalizing incident in which she had forced her way into Chaplin's posh house, held a gun on him, and so aroused both of them that they had promptly gone to bed together. This was around Christmas, 1942. Even more damaging: Joan said that in October, 1942, she had gone to New York City at Chaplin's expense, had been followed by him, and had had relations with him in his hotel room. This meant that Chaplin could be prosecuted under the Mann Act, a federal law which made it a serious crime (up to 25 years in prison and a fine of $25,000) to transport a female across a state line for immoral purposes. Originally aimed at organized prostitution ("white slavery"), the Mann Act was also used as a sort of "interstate intercourse act," a way of prosecuting people the authorities wanted to "get" for some other, not necessarily criminal, reason.” Reproduced from "The People's Almanac" Bombay Phenotype • Discovered in 1952 • Example of epistasis (type of gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus). • “H substance”- glycosphingolipid modified with carbohydrates to form A and B antigens. • hh genotype masks expession of the A and B alleles (recessive epistasis). • FUT1: fucosyl transferase. The recessive allele h prevents synthesis of complete H substance- lacks a fucose moeity so enzymes made by A and B alleles cannot add appropriate sugars • Functionally type O (donor only!) • Individuals with Bombay phenotype can only be transfused with blood from other Bombay phenotype individuals. ...
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