BSC 2010 Chapter Notes - Chapter 15: X-Inactivation, Drosophila Melanogaster, Nuclear Membrane
27 Aug 2016
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Mendel & chromosomes: chromosome theory of inheritance. Mendelian genes have specific loci (positions) on chromosomes. Recessive = mutant: wild-type normal or typical: w, mutant type not normal: w. Morgan studied flies: he studied drosophila melanogaster fruit fly, take 2 weeks to breed. Hundreds of offspring per fuck: only 4 pairs of chromosomes. Morgan"s results: he crossed wild type (red eyes) with a mutant (white eyes), but did not get mendelian results, gender or sex differences. Called sex-linked gene or trait: only f2 males = white eyes! Progressively weakening of muscles and loss of coordination: hemophilia. Blood that is unable to clot normally: due to absence of proteins required for proper clotting. Females = x inactivation: although females receive 2 copies of alleles, one chromosome becomes inactivated during embryonic development. Due to xx: chromosome inactivation is random. Inactivation is due to methylation: so both females and males are operating on only 1 sex chromosome, barr body inactivated chromosome condenses.
